To get a sum of every second digit, starting from the next to last in C-CodePudding

Im very new in the coding world, so maybe my suggestion to this function is not the best. But how I see it it should work, but it obviously doesn't. What do I do wrong?

//to do checksum
int sum = 0;
for (int i = 2; i <= d; i   )
{
sum = sum   ((int) (number / pow (10, i - 1)) % 10) * 2;
number = number / 10;

}

printf("%i", sum );

CodePudding user response：

#include <stdio.h>

int main()
{
    int sum = 0;
    int num = 4532199;
    while (num) {
        num /= 10;
        sum  = num % 10;
        num /= 10;
    }
    printf("sum=%d\n", sum);
}