Skipping digits of a number and adding the non-skipped ones in C-CodePudding

I'm trying to get every other digit from a user-inputted number. And then find their sum. For example, 123456. I want to get 5,3, and 1. Then find their sum. This is my function for that:

int getSum(long userInput) // user input being passed as an argument.
{
   long userInput1 = userInput;
   long sumOfNum = 0 ;

 while(userInput1 != 0)
    {
      userInput1 = userInput1 / 10;
      sumOfNum  = userInput1 % 10;
    }

  printf("%ld\n",sumOfNum);
}

This doesn't work for all of the numbers, for example; with 12345, I am expecting 6. But the output is 10.

Where did I go wrong?

[Edit- How I did it? (based on the answer from Fe2O3) I need another division. So:

 while(userInput1 != 0)
    {
      userInput1 = userInput1 / 10;
      sumOfNum  = (userInput1 % 10);
      userInput1 = userInput1 / 10; // this one
    }
   printf("%ld\n",sumOfNum);
   return sumOfNum;
}

CodePudding user response：

To get every other digit...

int getSum( long val ) {
    int sum = 0;
    for( val /= 10; val; val /= 100 )
        sum  = val % 10;

    printf( "%d\n", sum );

    return sum; // missed this in previous version
}

EDIT:

After it was pointed out that 'sum' went out of scope after the for() terminated, the code has been adapted to have fewer division operations.

CodePudding user response：

An alternative approach. Slower, but simpler to understand.

#include <stdio.h>
#include <string.h>

int getSum(long val) {
    char buf[40]; // Must be big enough, and 40 is big enough for 128 bit numbers
    sprintf(buf, "%d", val); // Convert to string
    
    int sum=0;
    for(int i=0; i<strlen(buf); i  )
        sum  = buf[i] - '0'; 
        
    return sum;
}