timestring.c

#include <stdio.h>

char* solution(int T) {
    int h, m, s;
    char *time_str;
   
    h = (T/3600);
    m = (T - (3600 * h)) / 60;
    s = (T - (3600 * h) - (60 * m));

    snprintf(time_str, 10, "%02i:%02i:%02i\n", h, m, s);
    return time_str;
}

int main() {
    char *answer = solution(7050);
    printf("%s", answer);
}