passcode.c

#include <stdio.h>

void init_input(int input[], size_t psize) {
    for (size_t i = 0; i < psize; i++) {
        input[i] = 99;
    }
}

int check_password(int *password, size_t psize, int *input) {
    for (size_t i = 0; i < psize; i++) {
        printf("%i | ", i);
        printf("%i, %i\n", password[i], input[i]);
        if (input[i] > 9) { return -2; } //Means that the input isn't long enough.
        if (password[i] != input[i]) { return -1; } // No need to check more digits.
    }
    return 1;
}
int main() {
    size_t psize = 4;
    int password[] = {1,3,3,7};
    int input[4];
    init_input(input, psize);
    input[0] = 1;
    input[1] = 3;
    input[2] = 3;
    input[3] = 7; // This would be your keypad input. Try fucking around with it.
    int val = check_password(&password, psize, &input);
    printf("%i\n", val);
    return 0;
}