USACO-T012: Prime Cryptarithm

/*
ID: mickyta1
TASK: crypt1
LANG: C++
*/

#include <bits/stdc++.h>
using namespace std;

const int N = 10;

int arr[N + 1];
bool isInSet[10];

bool checkSet(int x){
    while(x > 0){
        int lastDigit = x % 10;
        if(!isInSet[lastDigit]){
            return false;
        }
        x /= 10;
    }
    return true;
}

bool has3Digit(int x){
    return 100 <= x && x < 1000;
}

bool has4Digit(int x){
    return 1000 <= x && x < 10000;
}

int main(){

    freopen("crypt1.in", "r", stdin);
    freopen("crypt1.out", "w", stdout);

    int n;
    scanf("%d", &n);
    for(int i = 1; i <= n; ++i){
        scanf("%d", &arr[i]);
        isInSet[arr[i]] = true;
    }
    int cnt = 0;
    for(int a = 1; a <= n; ++a){
        if(arr[a] == 0){
            continue;
        }
        for(int b = 1; b <= n; ++b){
            for(int c = 1; c <= n; ++c){
                int fst = 100 * arr[a] + 10 * arr[b] + arr[c];
                for(int d = 1; d <= n; ++d){
                    if(arr[d] == 0 || !has3Digit(fst * arr[d])){
                        continue;
                    }
                    for(int e = 1; e <= n; ++e){
                        int snd = 10 * arr[d] + arr[e];
                        if(arr[e] == 0 || !has3Digit(fst * arr[e]) || !has4Digit(fst * snd)){
                            continue;
                        }
                        if(checkSet(fst * arr[d]) && checkSet(fst * arr[e]) && checkSet(fst * snd)){
                            ++cnt;
                        }
                    }
                }
            }
        }
    }
    cout << cnt << '\n';

    fclose(stdin);
    fclose(stdout);

    return 0;
}