aoc-2020/2.1.c

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

int main() {
    int count = 0;

    int pos1, pos2;
    char target;
    char str[100];
    while (scanf("%d-%d %c: %s", &pos1, &pos2, &target, str) == 4) {
        pos1--; pos2--;

        int char_count = 0;
        if (str[pos1] == target)
            char_count++;
        if (str[pos2] == target)
            char_count++;

        if (char_count == 1)
            count++;
    }
    printf("%d\n", count);

    return 0;
}