PROG-T1100: Codes

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

typedef long long lli;

const int N = 1e5;
const int PB = 11;

int powOfPB[3], num[3], one[1331], two[1331], three[1000];

int main(){

    powOfPB[0] = 1;
    powOfPB[1] = 11;
    powOfPB[2] = 121;

    int nNumber;
    scanf("%d", &nNumber);
    lli cnt = 0;
    for(int i = 1; i <= nNumber; ++i){
        int x;
        scanf("%d", &x);
        num[2] = x / 100 + 1;
        num[1] = x % 100 / 10 + 1;
        num[0] = x % 10 + 1;

        // Add Sum: One Digit
        for(int j = 0; j < 3; ++j){
            cnt += one[powOfPB[j] * num[j]];
            ++one[powOfPB[j] * num[j]];
        }
        // Subtract Sum: Two Digits
        for(int j = 0; j < 2; ++j){
            for(int k = j + 1; k < 3; ++k){
                cnt -= two[powOfPB[j] * num[j] + powOfPB[k] * num[k]];
                ++two[powOfPB[j] * num[j] + powOfPB[k] * num[k]];
            }
        }
        // Add Sum: Three Digits
        cnt += three[x];
        ++three[x];
    }
    cout << cnt;

    return 0;
}