/* Online Java - IDE, Code Editor, Compiler Online Java is a quick and easy tool that helps you to build, compile, test your programs online. */ //VERSION 1: //I have declared all variables class level and static to ensure //that the recursive method is kept tidy //this challenge also raises performance question to capture timings //to ensure I can test the execution time, I will add stopwatch.. //I used AI solely for this part and realised it was part of Java.lang //So added start() and stop() around the addition method call in main method //this will be my complete last objective. //I have not attempted this in any of my code executions so far //For moment, I am using long variable to ensure I can extend //the String to 2,147,483,648 characters (digits only!) //need be careful that MSD can become 10 as oppose to 9 //so allow a single digit buffer for this. //Also MSD = most significant digit. In 25, 2 is MSD. //NOTE, there will be lots conversions between Integer to String //(examples remainingPortionInteger => remainingPortionString) //this is to facilitate appending outcome into grandTotal //which unfortunately can not be an int or Integer since it does not facilitate //appending digit at the front. //NOTE, there will be lots conversions between Integer to String: //EXAMPLES will be usage of Integer.toString(integer variable) //NOTE, there will be lots conversions between String to Integer: //EXAMPLES will be usage of String.valueOf(integer variable) //ALSO the test cases are very aggressive. public class Main { //used for stop clock static long startTime; static long endTime; static boolean running; static long elapsed; static int lengthFirstNumber; //number digits wide. This will get shorter during recursion. static int lengthSecondNumber; //number digits wide. This will get shorter during recursion. //these will work in conjunction with substring of the number to obtain last digit static String lastDigitFirstNumber; static String lastDigitSecondNumber; //this is only variable I have little explanation at moment. //it captures the 9 (third MSD) turning into a zero.. before it enters checking for //streak of 9s // 39993 //+ 15 static int temp; //extremely difficult to provide meaningful name //if there is NO frontal number (i.e) total less than 10, expect 0 in firstDigitTotalDigits //if total is between 10 - 18(9+9), expect firstDigitTotalDigits=1 //crucial part of adding two digits together //In practice this is also the remainder static int firstDigitTotalDigits; //9 + 3 = 12 firstDigitTotalDigits=1 lastDigitTotalDigits = 2 static int lastDigitTotalDigits; static int total; //stores total of two digits //used to output the running grandtotal //similar to expectation of manually completing addition static String grandTotal=""; //all below variables are closely linked //in addition, if a number is wider with extra digits, those additional //MSD need to drop straight down into grandtotal under right conditions static String remainingPortion; //if a number is more than 1 digit wider than other number, //the LSD of this portion has to be excluded. (since in real life addition, this is subject to //change if a number is carried forward). //if for instance, this is 9, then 9+1 =0, and carry 1. //in practice this could go on if all the digits in remainingPortionInteger is 9! //so would need to catch this ArrayIndexOutOfBoundsException should //String exceed limit of the long static int remainingPortionInteger; //This is conversion of remainingPortionInteger into String static String remainingPortionString; //exactly this, least MSD of remaining portion of String number1 static int lastDigitNumberOneRemainingPortion; //exactly this, least MSD of remaining portion of String number2 static int lastDigitNumberTwoRemainingPortion; //these come into play in the first catch statement... //it does not know which caused the exception. //so the variable names need to be generalised to ensure user friendly name //to support calculations... static String number; static int lastDigitRemainingPortion; static int lengthNumber; static String lastDigitNumber; public static void start() { Main.startTime = System.nanoTime(); Main.running = true; } public static void stop() { Main.endTime = System.nanoTime(); Main.running = false; } public static long getElapsedTime() { if (running) { elapsed = System.nanoTime() - startTime; } else { elapsed = endTime - startTime; } return elapsed; } public static double getElapsedTimeInSeconds() { return getElapsedTime() / 1_000_000_000.0; } public static void main(String[] args) { System.out.println("Welcome to Online IDE!! Happy Coding :)"); System.out.println("Addition program, ensure String has maximum characters: " + "2,147,483,648"); //it now functions formatted as below (without whitespace) //ALTHOUGH NO VALIDATION HAS BEEN PROVIDED, //DO NOT INCLUDE WHITESPACES IN STRING WHATSOEVER //THIS REPLICATES THE CHALLENGE. //EXPECT ERRORS IF ATTEMPTED //THERE ARE LOTS TEST CASES, SINCE IT WAS REALISED THAT WHEN FIXING CODE, //CASES FAILED AND THEN PASSED, AND VICE VERSA //ALSO CAN CHANGE VARIABLE number2 to number1 and vice versa. //***PASS**** - 100*** via final test 3,4,6,7,9,10,21,23 //String number2="99"; //String number1= "1"; //***PASS**1764*** via final test 0,2,3,4,5,24 //String number2="993"; //String number1="771"; //PASS*****160****** - via final test 3,4,5,6,7,9,10,21,24 //String number2 = "136"; //String number1 = "24"; //PASS******846370032454542****** via final test 3,4,5,6,7,9,10,11,20,24 //String number2 = "846369999999999"; //String number1 = "32454543"; //PASS****82160**** via final test 3,4,5,6,7,9,10,11,12,24 //String number2 = "81636"; //String number1 = "524"; //PASS******* - 400219 via final test 3,4,5,6,7,9,10,11,13,15,17,18,19,20,24 //String number2 = "399627"; //String number1 = "592"; //pass********* - 400019 via final test 3,4,5,6,7,9,10,13,15,17,18,19,20,24 //String number2 = "399947"; //String number1 = "72"; //PASS***4962****** getting via final test 3,4,5,6,7,9,21,24 //String number2 = "3970"; //String number1 = "992"; //PASS****** 562 via final test 0,1,3,4,5,24 //String number1 = "370"; //String number2 = "192"; //PASS**** - 1000 via final test 2,3,4 //String number2 = "999"; //String number1 = "1"; //PASS***** 1998 via final test 2,3,4 //String number1 = "999"; //String number2 = "999"; //PASS ******* 1098 via final test 3,4,6,7,8,10,21,24 //String number1 = "999"; //String number2 = "99"; //***PASS***108 via final test 3,4,6,7,17,24 //String number1 = "99"; //String number2 = " 9"; //***PASS**** 1400019 via final test 3,4,5,6,7,9,10,11,13,15,17,18,19,20,24 //String number2 = "1399947"; //String number1 = "72"; //***PASS****5210*** via final test 3,4,6,7,9,10,21,24 //String number2 = "4666"; //String number1 = "544"; //***PASS***711**** via final test 3,4,6,7,9,21,24 //String number2 = "652"; //String number1 = "59"; //PASS****1390219 ***** via final test //String number2 = "1389627"; //String number1 = "592"; //PASS***********22023**** via final test 3,4,6,7,8,10,11,13,15,17,18,19,20,24 //String number1 = "21999"; //String number2 = "24"; //PASS****2******* via final test 1,3,5,24 //String number1 = "1"; //String number2 = "1"; //PASS***10******** via final test 2,3,4,24 //String number1 = "1"; //String number2 = "9"; //PASS***95759******** via final test 3,5,6,7,8,10,11,12,24 //String number1 = "95427"; //String number2 = "332"; //PASS*****9719****** via final test 3,4,5,6,7,8,10,11,12,23 //String number1 = "9647"; //String number2 = "72"; //PASS****100119******* via final test 3,4,6,7,8,10,11,13,15,17,18,19,20,24 //String number1 = "99647"; //String number2 = "472"; // **PASS** 10009 via final test 3,4,6,7,8,10,11,13,15,17,18,19,20,24 //String number1 ="9947"; //String number2 = " 62"; //PASS via final test 3,4,6,7,8,10,11,13,15,17,18 //***PASS 22023 //String number1 = "21999"; //String number2 = "24"; //PASS via final test 3,4,6,7,8,21,24 //String number1 = "99"; //String number2 = "9"; //FAIL getting 10100 (identified during late late testing) //String number1 = "999"; //String number2 = "1"; //PASS via final test 3,5,6,7,8,11,12,24 String number1 = "888"; String number2 = "1"; //PASS //String number1 = "99999999999999999999999999999999999999999999999999999999"; //String number2 = "32423543534543532423432423432494355443534532235324324333"; //For an unknown reason, the addition method is unable to return the String, it just shows blank value //or just skips the return statement (proven by recursive method terminating) and returning test //to method invocation in main. //Good news is that it does not branch off elsewhere in the code. //Bizarre is that it can see the variable value on screen before I try to return it. //So I have just used System.out.println(GRANDTOTAL) in recursive method. //it will be proven since the code will officially return last return statement. start(); System.out.println(number1 + "+" + number2 + "= " + addition(number1, number2)); System.out.println(number1 + "+" + number2 + "= " + grandTotal); stop(); System.out.println("Elapsed time in seconds: " + getElapsedTimeInSeconds()); } public static String addition(String number1, String number2) { //it is still working constraints of the code //the Strings are not being converted to simplify addition, //it is only the length of the Strings. lengthFirstNumber=(number1.length()); lengthSecondNumber=(number2.length()); /* //at this point it knowws that its on the most extreme left hand side of them... //looking at example 4666 // + 544 //it is just not a case of dropping the number 4 down.... into the grandTotal //this would be ok if (6+5 was not >=10) //there would be last addition undertaken //at this point its expected to perform 4 + //another example is just a case of dropping the remainder across //for instance performing 55 + 55 ------- 110 ------- //Another example is dealing with larger differences: 274666 + 544 //it would need to carry 1, add it to 4 //it would then have to truncate number1 again and drop 2 and 7 */ //if both lengths are 0, it means both had same lengths. if (lengthFirstNumber==0 && lengthSecondNumber==0) { //this is a slightly ambiguous name, but it identifies if //total from digit in number1 number2 is one or two digits long //firstDigitTotalDigits = (int)total/10; //if there is no frontal number (i.e) total less than 10, expect 0 in firstDigitTotalDigits //if total is between 10 - 18(9+9), expect firstDigitTotalDigits=1 //REFERS TO NO CARRY FORWARD, THIS SEEMS CORRECT //SINCE IT WOULD HAVE NOT BRANCHED OFF TO ANY TRY/CATCH STATEMENTS System.out.println("final test 0"); if (firstDigitTotalDigits==0) { System.out.println("GRANDTOTAL: " + grandTotal); System.out.println("FINAL TEST 1"); return grandTotal; } // THIS APPEARS CORRECT SINCE IT WOULD HAVE NOT HIT ANY CATCH STATEMENT //SO IT IS IN MAIN CODE FLOW //IT WOULD HAVE ADDED lastDigitTotalDigits into grandTotal //just a case of adding extra 1 since no more digits left in number1 or number2 //AND if the firstDigitTotalDigits is not 0, it has to be 1 else { System.out.println("FINAL TEST 2"); //it would append a 1 to the left of existing MSD grandTotal = "1" + grandTotal; System.out.println("GRANDTOTAL: " + grandTotal); return grandTotal; } } //unfortunately variable names are extremely confusing //need to remember it takes values from here onwards with one argument //if number1 was 9123 lengthFirstNumber=4 //there is a digit at index 3, so variable is reduced by 1 System.out.println("**THIS IS ADDITION**********"); System.out.println(number1); System.out.println(number2); //need try here since it was giving NumberFormatException and //StringIndexOutOfBoundsException (explained in catch statement) //why these could occur //note, it would have already dealt with circumstance of processing all //digits in both uniform numbers above in first loop in addition method. //So would not be here if this was not case try { System.out.println("final test 3"); //if number1 was 1234 lengthFirstNumber=4 //performing number1.substring(3) would get single digit from index position 3 //note that number1 and number2 are shrinking as part of the process //so it always relative to same last index //it replicates simulation of moving across right to left in real life lastDigitFirstNumber=number1.substring(lengthFirstNumber-1); lastDigitSecondNumber=number2.substring(lengthSecondNumber-1); //as you would expect to add those digits above total = Integer.valueOf(lastDigitFirstNumber) + Integer.valueOf(lastDigitSecondNumber) + firstDigitTotalDigits; //checks if the total is greater than 10. This is the same index on number1, number2 and also //carry forward 1 if applicable if ((Integer.valueOf(lastDigitFirstNumber) + Integer.valueOf(lastDigitSecondNumber) + firstDigitTotalDigits)>=10) { System.out.println("\nOVER 10"); System.out.println("final test 4"); System.out.println("addition of: " + Integer.valueOf(lastDigitFirstNumber) + " + " + Integer.valueOf(lastDigitSecondNumber)); System.out.println("this is current total: " + total); //first digit carried forward, only feasible value is 1 since total greater than 10 firstDigitTotalDigits = (int)total/10; System.out.println("This is first digit, it will be carried forward: " + firstDigitTotalDigits); //getting last digit in total (10-18), lastDigitTotalDigits is between 0-8 lastDigitTotalDigits=total%10; //it has to be stored in grandTotal on the most left hand side (MSD) like real life //note it is not overwriting existing value grandTotal = Integer.toString(lastDigitTotalDigits) + grandTotal; System.out.println("running grand total: " + grandTotal); //recursive call. It truncates numbers by one digit as described above addition(number1.substring(0, (lengthFirstNumber-1)), number2.substring(0, (lengthSecondNumber-1))); } else { //we expect total to be a single digit ///same principle above, added to left of existing MSD grandTotal = Integer.toString(total) + grandTotal; System.out.println("final test5"); System.out.println("\nless than 10"); System.out.println("addition of: " + Integer.valueOf(lastDigitFirstNumber) + " + " + Integer.valueOf(lastDigitSecondNumber)); System.out.println("this is current total: " + total); System.out.println("running grandtotal: " + grandTotal); //it needs to set the carry forward value to 0 firstDigitTotalDigits=0; //same style recursive call addition(number1.substring(0, (lengthFirstNumber-1)), number2.substring(0, (lengthSecondNumber-1))); } } //it would enter here if issue processing: //REASON for StringIndexOutOfBoundsException if either //lengthFirstNumber or lengthSecondNumber were 0 //lastDigitFirstNumber=number1.substring(lengthFirstNumber-1); //lastDigitSecondNumber=number2.substring(lengthSecondNumber-1); //REASON for NumberFormatException //Since if no value in either (NOT BOTH) Strings (lastDigitFirstNumber //or lastDigitSecondNumber) // it can not get Integer value henceforth. //Integer.valueOf(lastDigitFirstNumber) //Integer.valueOf(lastDigitFirstNumber) catch (NumberFormatException | StringIndexOutOfBoundsException s) { System.out.println("final test 6"); System.out.println("123This is last digit first number:" + lastDigitFirstNumber); System.out.println("123This is last digit second number:" + lastDigitSecondNumber); //now in here, it has to check if there is a carry over of 1 //if so it would add it to last digit of either number1 or number2 //for initial numbers such as, it is fortunately relatively more straight forward //4636 //+ 524 //but it was in a try and catch since if any of the values: //lastDigitFirstNumber="" or lastDigitSecondNumber="" //it would cause NumberFormatException since it can not format String => int //if the String is empty! We know however ONLY one of them is empty //if ((Integer.valueOf(lastDigitFirstNumber) + Integer.valueOf(lastDigitSecondNumber) //the alternate technique would be to add 0's on the front of the shortest number //to ensure both have uniform length, however this would affect readability when performing //System.out.println() //it is imaginary thought process and perhaps would have solved lots of these //exceptions. But I feel other logic going forward might have been disrupted also. //still in catch, processing non uniform numbers.. System.out.println("number 1 at this point: " + number1); System.out.println("number 2 at this point: " + number2); //for instance in these numbers below, it would reach here and //lastDigitSecondNumber=3 and lastDigitFirstNumber=2 //it has not been able to progress to lastDigitSecondNumber=1 and //lastDigitFirstNumber since lastDigitFirstNumber has no value. //if I try to use these variables again, it would be a loop of errors. //A solution is to fill a 0 here, but once again I am refraining from this //to ensure screen readability mimics calculation in real life. //number2 = "136"; //number1 = "24"; //so now, it can no longer examine lastDigitFirstNumber or lastDigitSecondNumber //focus will be on number1 and number2 (string itself.) try { System.out.println("final test 7"); System.out.println("number1: " + number1); System.out.println("number2: " + number2); //NOTE BOTH CAN NOT BE BLANK! System.out.println("This is lastDigitSecondNumber: " + lastDigitSecondNumber); System.out.println("This is lastDigitFirstNumber: " + lastDigitFirstNumber); System.out.println("REMAINDER RIGHT NOW: " + firstDigitTotalDigits); //it is not sure which number is null, so rather than copying the //code in if number2!=null into similar if statement (number1!=null), //variables created to be generic to both scenarios: //this will also allow me to flip the variable names in test case variable declarations //without worrying if number1 is longer than number2 or which has streaks of 9 System.out.println("num1: "+ number1); System.out.println("num2: " + number2); //length of one number will be greater than the other //number variable is just the remaining portion of number. //lastDigitRemainingPortion variable takes % of number //lengthNumber is length of the number if (number1.length()>number2.length()) { System.out.println("final test 8"); System.out.println("GONE INTO NUMBER1 NOT NULL"); number=number1; lastDigitRemainingPortion = lastDigitNumberOneRemainingPortion; lengthNumber=lengthFirstNumber; //note this variable is opposite, will be evident later lastDigitNumber=lastDigitSecondNumber; } //same explanation as above for variables if (number2.length()>number1.length()) { System.out.println("final test 9"); System.out.println("GONE INTO NUMBER2 NOT NULL"); number=number2; lastDigitRemainingPortion = lastDigitNumberTwoRemainingPortion; lengthNumber=lengthSecondNumber; //note this variable is opposite, will be evident later lastDigitNumber = lastDigitFirstNumber; } //it no longer matters if EITHER number1 or number2, ready to handle //both scenarios if (number!=null) { System.out.println("final test 10!!!!!!!!"); //if this is the case, it has to get the last digit //and perform addition on this alone as per usual.... if(number.length()>1) { System.out.println("final test 11 "); //taking % gets last digit lastDigitRemainingPortion = (Integer.valueOf(number)%10); System.out.println("lastDigitRemainingPortion: " + lastDigitRemainingPortion); //at this point, we still need to //have lots consideration. Before above it would carry across the //firstDigitTotalDigits (which would be 1 if total is 10-18) //if no extra logic is applied, it will perform: //String number2 = "9947"; //String number1 = "72"; //7+2 = 9 (grandtotal = 9) //4+7= 11 (store 1 and carry 1 across) (grandtotal = 19) //9+1 = 10 (it will not carry anything) (grandtotal = 1019) (INCORRECT) //drop the last digit number1 (grandtotal = 91019) (INCORRECT) //it is NOW difficult to send it back to above loop for recursion... //option is to create a boolean flag and force it back here. //better option for understanding is to hardcode this logic in again //and take a performance hit. //if total is less than 10, it can simply get total and drop numbers like above //total as usual, full visibility of firstDigitTotalDigits from legitimate calculation //on last digit at uniform location in number1 and number2 System.out.println("lastdigit remaining portion:" + lastDigitRemainingPortion); total = Integer.valueOf(lastDigitRemainingPortion) + firstDigitTotalDigits; //for example explaining below: 9647 // + 72 //6+ 1 (carried forward) is less than 10. if (total<10) { System.out.println("WHAT IS TOTAL: " + total); System.out.println("final test 12"); //drops off last digit remaining portion remainingPortionInteger = (int) (Integer.valueOf(number) / 10); remainingPortionString = Integer.toString(remainingPortionInteger); System.out.println("1This is remaining portion after conversion: " + remainingPortionString); remainingPortion = remainingPortionString.substring(0, (lengthNumber-1)); System.out.println("This is remaining part: " + remainingPortion); //this is not applicable to both scenarios.... //this is applicable to if single carry forward does not cause MSD to exceed //9 //it can simply drop down 9 (as per example outside this loop) //(or infact the entire remainingPortion) since total (6+1 is less than 9) grandTotal = remainingPortion + Integer.toString(total) + grandTotal; System.out.println("GGGGRANNND TOTAL: " + grandTotal); return grandTotal; } //total is greater than or equal to 10 (inner 9+1) //NOTE, the total can not exceed 10 anymore //since 1 is maximum firstDigitTotalDigits //and not uniform number1 and number2 //this else loop will get very involved later on. //since the carry forward could have a knock on effect //if the upcoming MSD are 9's! //number1 = "99647"; //number2 = "472"; else { System.out.println("final test 13"); System.out.println("1GREATER!!!!!!!!!"); firstDigitTotalDigits=(int) total/10; //expecting to get a 1 System.out.println("This is the carry forward: " + firstDigitTotalDigits); lastDigitTotalDigits=total%10; //number between 0 and 8 //expecting a 1 here since it has removed lastDigitTotalDigits remainingPortionInteger = (int) (Integer.valueOf(number) / 10); System.out.println("should be: " + remainingPortionInteger); //we need this number to ascertain what actions required with a remainder //if this is a 9, we know that firstDigitTotalDigits is definitely 1, //it will force 9+1 and store 0 into grandTotal lastDigitRemainingPortion =Integer.valueOf(Integer.valueOf(number)%10); System.out.println("WHATSSSSS: " + lastDigitRemainingPortion); //NOT ENTIRELY SURE IF THIS IS CORRECT EXAMPLE// //it would enter in similar situation but not // "9627" "927" // + "92" + "92" //System.out.println("CONFIRM RIGHT TRACK TOTAL GREATER THAN 10: " + number2.substring((lengthSecondNumber-1))); //no cascading effect //it would know that even if carry 1 forward was applicable, //it would stay single digit //NEED to be careful and understand that if remainder firstDigitTotalDigits was 0 (6+2=8) //The 9 in number.substring(lengthSecondNumber-1) would still be valid //since it would not be affected. //IT IS BIT ODD THAT THIS NEXT CONDITION BLOCK WAS A VALID CODE SEGMENT DURING MODIFYING MY CODE TO COMPLETION, //BUT CAN NOT FORCE IT BACK HERE AGAIN //IT HAS BEEN OVERRIDEN SOMEWHERE, AT MOMENT JUST NOT SURE //IT FAILS TO ENTER HERE IN ALL MY TEST CONDITIONS //FOR MOMENT I AM MANTAINING THE CODE //Tried to investigate exactly where it was at //System.out.println("still ft9: " + number); //System.out.println("still ft9 remainder: " + firstDigitTotalDigits); //System.out.println("still ft9: " + (lengthNumber-1)); //System.out.println("still ft9: " + Integer.valueOf(number.substring((lengthNumber-1)))); //System.out.println(remainingPortionInteger); if (((Integer.valueOf(number.substring((lengthNumber-1)))+firstDigitTotalDigits)<10)) { System.out.println(grandTotal + " so far"); System.out.println("final test 14"); System.out.println("£££££££££££££££££"); //System.exit(0); //we know there wont be cascading effect... //this would do 6 + carry forward), //remainingPortion(MSD) into grandtotal. On this instance it would be 9 //(9647 // + 72) total = lastDigitRemainingPortion + firstDigitTotalDigits; //this will put the remainingpart(9) + total (9 + 0 carried forward) + existing grandTotal grandTotal = remainingPortionInteger + total + grandTotal; System.out.println("G: " + grandTotal); //it would now truncate single digit of number 2 //and place this in the grandtotal System.out.println("WHAT IS NUMBER RIGHT NOW:" + number); } //there will be minimum 1 cascading effect //for instance 19947 // + 62 else { //at this point it has to examine all the remainingPortion (19) //backwards since if there are multiple 9 this will keep cascading... //a good starting point is being here and acknowleding there is a single cascading effect //at minimum System.out.println("final test 15"); //System.out.println(remainingPortionInteger); System.out.println("123****** REMAINING ****: " + number); System.out.println(number.substring((lengthNumber-1))); System.out.println(firstDigitTotalDigits); //this can only be a single digit of 9 remaining //it would simply perform 9 + 1 = 10. //for example //947 //+ 62 if(lengthNumber==1) { System.out.println("final test 16"); //total HAS to be 10 //we expect a value in carry forward firstDigitTotalDigits since it would be //9 appearing straight away after the lengths processed (at uniform MSD location) in //number1 and number2 remainingPortionInteger=Integer.valueOf(number); //there is a single digit hence number2 can be taken as a whole. total = remainingPortionInteger + firstDigitTotalDigits; //it can now be placed into grandtotal grandTotal = Integer.toString(total) + grandTotal; } //this is almost a recursive do while loop without calling //recursive method. //I am not sure if this is within restrictions of the challenge //but its not practical to call the addition recursive method again.. //it can perhaps be undertaken by setting up a flag perhaps consecutiveNines //but I think its best to keep flow going downwards than to move upwards.. //more than 1 digit remaining //and whilst they are all 9s //same scenario as above but extra 9 //9947 //+ 62 //This was the most challenging part of the code. //It has created some disagreement in my thought process //but it was expected when branching this deep. else { System.out.println("final test 17"); //in practice it should still have the record of firstDigitTotalDigits //and we know it is not 0 otherwise //it would have executed this loop (since 9 + 0 <10) //if (((Integer.valueOf(number2.substring((lengthSecondNumber-1)))+firstDigitTotalDigits)<10)) //ok to set it again, but this only adds to confusion. Not required firstDigitTotalDigits=1; //also need to remember that currently still within //massive else statement of the extra digit in number2 equalling //10 (with 1 carry forward). //for instance the 39 part left of the number // 3974 // + 45 //This now includes entire block //note number2 has not got shorter at all yet //It might be worth looking at addition such as, which would bring us here //number1 = "21999"; //number2 = "24"; //these are key variables which dictate calculations... //Grand total is 23 //Number so far is 219 //remainingPortionInteger = 21 //this tells us no processing has occured for the 9s System.out.println("GRAND TOTAL SO FAR: " + grandTotal); System.out.println("NUMBER SO FAR: " + number); System.out.println("REMAINING PORTION INTEGER SO FAR: " + remainingPortionInteger); System.out.println("last digit remaining portion: " + lastDigitRemainingPortion); //this now removes the last digit. remainingPortionInteger = (int) (Integer.valueOf(number))/10; //since it has not processed the digit removed above from number, //it needs to store it first. It would be storing 9 for instance. temp=Integer.valueOf(number)%10; System.out.println("The number:" + number); System.out.println("remaining portion integer:" + remainingPortionInteger); //it takes a digit off the end off 21. lastDigitRemainingPortion = remainingPortionInteger % 10; System.out.println("WHAT is lastDigitRemainingPortion now: " + lastDigitRemainingPortion); //this now processes the number of consecutive 9s found //This is the first iteration used in the code. //It requires addressing. do { //still at this point, based on: //number1 = "21999"; //number2 = "24"; //remainingPortionInteger = 21 //grand Total = 23 //lastDigitRemainingPortion = 1 //So it will skip this next if loop (final test 15) //but it has to be questioned, why was last digit removed //if it enters this loop for the first 9 situation with //consecutive 9s, it will also shrink the variable //remainingPortionString (based on remainingPortionInteger) //I have tried to comment out the lines above: //temp=Integer.valueOf(number)%10; //lastDigitRemainingPortion = remainingPortionInteger % 10; //But what happens is that it breaks out of the do while loop //it reaches bottom of code and performs: //grandTotal = total + grandTotal; We know it should actually //drop the (remainingPortionInteger + 1) = 22 //But instead it drops 10, so the answer for 21999+24 = 1023 //I also set up a boolean so that it can apply correct logic //if it went into lastDigitTotalDigits=9 (i.e commenting out lastDigitTotalDigits). //in which case grandTotal would be 019 //and if the flag is set it would drop the 22 in front of 019 //But this had massive impact when performing calculations //such as 99 + 9 (since remainingPortionInteger was null) //this in effect meant I had to change my code in these areas. //In effect, I created another version of the code for this. //Both codes are functional, version 2 seems more correct logically //But this version has less loop branching. //But codes unfortunately need to insert a 0 or 9 respectively //out of context of the variable.. //System.out.println("\nfinal test 14"); //System.out.println("remainportion: " + remainingPortionInteger); //System.out.println("GRAND TOTAL---:" + grandTotal); //System.out.println("last dig pos: " + lastDigitRemainingPortion); System.out.println("\n\nfinal test 18"); //this begins to write a 0 for every 9 that it finds in remainingPortionInteger grandTotal = Integer.toString(total) + grandTotal; //this will get shorter by a digit each time remainingPortionInteger = remainingPortionInteger/10; //at same time expecting a 9 to be filled on left hand side and carry over //this is so that once it breaks out of the loop, //it has a total of MSD before the 9. //We know the previous MSD would have been 9+1 = 0 //so it includes the lastDigitNumberTwoRemainingPortion //to speed up execution, this is also better option //total = 0; // (equivalent to 9+1 and obtaining last digit) //prevents calculation below. total = lastDigitRemainingPortion + firstDigitTotalDigits; //it will now get new last digit //the purpose of this is so that once it finishes the do while loop //of storing 9s, it can process anything else left //remainingPortionInteger lastDigitRemainingPortion = remainingPortionInteger%10; System.out.println("bf: " + lastDigitRemainingPortion); System.out.println("\nnew grand total: " + grandTotal); }while(lastDigitRemainingPortion==9); System.out.println("final test 19"); //at this point the remaining number could be: //8 or it could be 888888888 //But we know definitely that there is no longer a cascade for the //grandtotal //converts remaining portion to String for usage in grandTotal remainingPortionString=Integer.toString(remainingPortionInteger); //it adds 0 unaccounted for(before entering do while loop which shortened //remainportionInteger), this is result of 9 + carry forward of 1 // Note the 0 is LSD before the remainingPortionString //we know the remainingPortionString can be dropped into grandTotal //due to no cascading effect if (temp==9) { System.out.println("final test 20"); total = Integer.valueOf(remainingPortionString) + firstDigitTotalDigits; grandTotal = total + "0"+ grandTotal; System.out.println("GRAND - :" + grandTotal); return grandTotal; } } //end of else final test 17 }//end of else final test 15 }//end of else final test 16 }// this would be end final test 11 for if(number.length()>1) //this would be else of the above. //so number.length<=1 else { System.out.println("DOUBLE CHECK REMAINDER: " + firstDigitTotalDigits); System.out.println("final test 21"); System.out.println(lastDigitNumber); total = Integer.valueOf(lastDigitNumber) + firstDigitTotalDigits; System.out.println("uuTOTAL NOW: " + total); //this would be 1 digit wide so ok to use this //as oppose to lastDigitNumber remainingPortionInteger= Integer.valueOf(number); System.out.println("REMAINING PORTION: " + remainingPortionInteger); //this will just simply take the number and any carry forward from previous MSD total = remainingPortionInteger + firstDigitTotalDigits; System.out.println("TOTALLLL: " + total); grandTotal = total + grandTotal; System.out.println("GRANDDDD TOTAL: " + grandTotal); return grandTotal; } //at this point we have dealt with scenarios such as these since it has logic //to carry forward 1 // 4636 // + 324 // 4636 // + 524 //but if the numbers were: 84636 // + 524 //it would fail since it has not had opportunity to process the 8 in number1 //so simply, once it has performed total with 4 and no value in number2 //it needs to take all the remaining numbers in the substring //and append it to the grand total //in effect it will shorten length number again by 1.. //note this time the shortening is normal. } // this is the end of number!=null } //end try //exactly same as above, but flipped to number1 //catch (NumberFormatException | StringIndexOutOfBoundsException s) //I have bypassed this by setting up generic variables as described in declarations catch (NumberFormatException n) { System.out.println("final test 22"); //this was previously reserved for performing operation when //number1!=null //but I changed logic as described in the try. //so strictly speaking, the whole try structure above can be removed. } //hard to explain reason for this code //would expected everything to be in if-else //would need to verify it enters here part of testing. System.out.println("FFFFFtotal: " + grandTotal); System.out.println("remaining portion: " + remainingPortion); System.out.println("total: " + total); System.out.println("final test 23"); //LAST ADDITION - CAREFUL grandTotal = total + grandTotal; System.out.println("grand23333: " +grandTotal); return grandTotal; } //end of catch (NumberFormatException | StringIndexOutOfBoundsException s) System.out.println("final test 24"); return "test"; } //end of main method }//end of class main