字符没有使用 atoi() 添加为整数？

Question

I'm new to C. I have a very silly question, but I can't figure out this very simple bug in my code for generating combinations.

#include <stdio.h>
#include <stdlib.h>
#include <time.h>

void combinations (int v[], int start, int n, int k, int maxk) {
        int i;

        if (k > maxk) {
                
                for (i=1; i<=maxk; i++) {
                  int sum = 0;
                  sum += v[i];
                  printf("%d", sum);
                }
                
                printf ("\n");
                return;
        }
        
        for (i=start; i<=n; i++) {
                v[k] = i;
                combinations (v, i+1, n, k+1, maxk);
        }
}

int main (int argc, char *argv[]) {
        int v[100], n, k;
        n = atoi (argv[1]);
        k = atoi (argv[2]);
        combinations (v, 1, n, 1, k);
        exit (0);
}

If you run the code above using ./main 5 3 , you'll get the following:

123
124
125
134
135
145
234
235
245
345

What I was trying to do was print out the sum of the integer representations, not the concatenated characters - for instance, the first line should be 6 , not 123 . Unfortunately, I'm getting a weird error when ever I use atoi() on the line sum += v[i]; , eg sum += atoi(v[i]); throws an error. I know I can't really use atoi() because I don't have a pointer, but I'm not sure how to resolve this problem. Using int(v[i]) doesn't throw an error, but it also doesn't fix the problem.

I'd greatly appreciate if someone could 1) tell me why atoi() isn't appropriate here/how I'm using it wrong and 2) how I can get each element of each combination to be treated as an integer.

Answer 1

The following loop is resetting sum on every iteration, so all it's doing is adding v[i] to 0 each time. It's also printing sum on every iteration, rather than once at the end:

for (i=1; i<=maxk; i++) {
    int sum = 0;
    sum += v[i];
    printf("%d", sum);
}
printf ("\n");

Just change it to:

int sum = 0;
for (i=1; i<=maxk; i++) {
    sum += v[i];
}
printf("%d\n", sum);