PROG-T1017: Magic Square

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

const int N = 10;
const int N2 = N * N;

int board[N + 10][N + 10];
bool found[N2 + 10];

int main(){

    int n;
    scanf("%d", &n);

    int crossSumL = 0;
    int crossSumR = 0;
    int lastSum;
    for(int i = 1; i <= n; ++i){
        int rowSum = 0;
        for(int j = 1; j <= n; ++j){
            scanf("%d", &board[i][j]);
            found[board[i][j]] = true;
            rowSum += board[i][j];
            if(i == j){
                crossSumR += board[i][j];
            }
            if(i + j == n + 1){
                crossSumL += board[i][j];
            }
        }
        if(i == 1){
            lastSum = rowSum;
        } else if(rowSum != lastSum){
            cout << "No";
            return 0;
        }
    }
    if(!(crossSumL == crossSumR && crossSumL == lastSum)){
        cout << "No";
        return 0;
    }

    for(int i = 1; i <= n; ++i){
        int colSum = 0;
        for(int j = 1; j <= n; ++j){
            colSum += board[j][i];
        }
        if(colSum != lastSum){
            cout << "No";
            return 0;
        }
    }

    int n2 = n * n;
    for(int i = 1; i <= n2; ++i){
        if(!found[i]){
            cout << "No";
            return 0;
        }
    }
    cout << "Yes";

    return 0;
}