Recursion, possible error in algo

Question

i am doing one of the simple programin C, sum of digits of 5 digit number.Though i had done it using a simple function but i need to do it with recursion also.I had read many solution on net regarding this problem using recursion and had implemented one of mine.But that is giving error and i cant figure out what mesh i am doing in my algo.

#include<stdio.h>
int sum5(int x);  //function for sum of  digits of 5 digit number

int main()
{
   int x;
   int result;
   printf("Enter a 5 digit number : ");
   scanf("%d",&x);
   printf("Number entered by you is %d",x);
   result = sum5(x);
   printf("Sum of digits of 5 digit number is = %d",&result);
   return 0;
}

int sum5(int x)
{
   int r;
   int sum=0;
   if(x!=0){
      r=x%10;
      sum=sum+r;
      x=x-r;      //doing this so that 0 come in the last and on diving it by 10, one digit will be removed.
      sum5(x/10);
   }
   return sum;
}

but after its execution i am getting wrong result.It is dumping some anonymous value on the output.

this part is useless x=x-r; as what youre sending afterwards will anyway remove the right-most digit. it wont work as no one gets the return value from the recursion call. — Ariel Pinchover
– Ariel Pinchover, Commented May 9, 2013 at 12:14

Osiris · Accepted Answer · 2013-05-09 12:13:56Z

8

Also, your sum5 function is incorrect. You have to add the value of sum5 to the sum variable of the caller function.

int sum5(int x)
    {
        int r;
        int sum = 0;
        if (x != 0) {
            r = x % 10;
            sum = r;
            //x = x - r;  - this isn't required. integer division will floor x
            sum += sum5(x / 10);
        }
        return sum;
    }

answered May 9, 2013 at 12:13

Osiris

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1 Comment

shailendra Over a year ago

@0A0D: i had tried it with my code, basically with &result error i wasnt adding the result of recursion.But now its working fine

Community · Accepted Answer · 2017-05-23 10:25:13Z

8

This is incorrect as it is printing the address of result and not its value:

printf("Sum of digits of 5 digit number is = %d",&result);

Change to:

printf("Sum of digits of 5 digit number is = %d", result);

Always check the result of scanf() to ensure a valid value was read:

/* Returns number of assignments made. */
if (scanf("%d", &x) == 1 && x > 9999 && x < 100000)
{
}

Plus the error in the implementation of sum5() as pointed out by Osiris .

edited May 23, 2017 at 10:25

CommunityBot

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answered May 9, 2013 at 12:10

hmjd

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1 Comment

shailendra Over a year ago

Yes that &result was a silly mistake though.And that if(scanf("%d",&x)==1){} this found to be very useful.

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