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Thread: Returning wrong value without modifying!!

  1. #1
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    Default Returning wrong value without modifying!!

    Iam trying to solve a question.The question is
    Finding sum of digits of a number until sum becomes single digit.
    .
    Example
    Input : 12345
    Output: 6

    The individual digits should be added untill it become single digit.1+2+3+4+5=15 -->1+5=6.

    In the below code the input is:
    i)first line number of test cases
    ii)second line is the number.

    When I run the code , the following are the inputs Iam giving:
    1;
    12345;
    The output should be "6" but it is printing "15".It is not printing "6".Iam unable to understand what's wrong woth the below code.Plz. help!!

    import java.util.Scanner;
    class AddNum{
     
    	public int  Add(int num) {
    		int x;
    		int sum=0;
    		int rem;
     		while(num>0) {
     
    			rem=num%10;
    			sum=sum+rem;
    			num/=10;
    		}
    		if(sum>9) {
    			Add(sum);
    		}
    		return sum;
     
     
    	}	
    }
     class IndividSum {
     
    public static void main(String[]  args)throws Exception{
    	Scanner sc=new Scanner(System.in);
    	int test=sc.nextInt();
    	AddNum obj=new AddNum();
    	int num[]=new int[test];
    	int Ans[]=new int[test];
    	for(int i=0;i<test;i++) {
    		num[i]=sc.nextInt();
    	}
    	for(int i=0;i<test;i++) {
    		Ans[i]= obj.Add(num[i]);
    		System.out.println(Ans[i]);
     
    	}
    sc.close();
    }
     
    }

  2. #2
    Super Moderator Norm's Avatar
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    Default Re: Returning wrong value without modifying!!

    How are you debugging the code to see where it is going wrong?

    Add some print statements that print out the values of variables as the code changes their values and uses them. The print out should show you what the computer sees when it executes and help you find the problem.
    If you don't understand my answer, don't ignore it, ask a question.

  3. #3
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    Default Re: Returning wrong value without modifying!!

    Actually the sum value in class AddNum is 6 but when the value is returned to Ans[i] in class IndividSum,it is showing 15.My question is why is it returning wrong value?

  4. #4
    Super Moderator Norm's Avatar
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    Default Re: Returning wrong value without modifying!!

    why is it returning wrong value?
    You need to debug the code to see what it is doing so you can find the problem.
    I suggested adding print statements to the code so you can see what it is doing. The print out will help you find the problem.

    Can you copy the full contents of the debug printout that shows what the code is doing and paste it here?
    If you don't understand my answer, don't ignore it, ask a question.

  5. #5
    Junior Member tonya's Avatar
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    Default Re: Returning wrong value without modifying!!

    the problem is in your recursion, when it backs out sum is the old value, you need to change your recursive call to:
    if(sum>9) {
    	sum = Add(sum);
    }

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