Envío 875

Código

#include <iostream>
#include <vector>
using namespace std;

bool solve(int N, vector<vector<int>> matrix, int diag1, int diag2) {
  if (diag1 != diag2) {
    return false;
  }
  if (matrix[0][N - 1] != diag1 or matrix[N - 1][0] != diag1) {
    return false;
  }
  for (int i = 1; i < N; ++i) {
    if (matrix[N - 1][i] - matrix[N - 1][i - 1] != diag1) {
      return false;
    }
    if (matrix[i][N - 1] - matrix[i - 1][N - 1] != diag1) {
      return false;
    }
  }

  return true;
}

int main() {
  int N;
  cin >> N;
  vector<vector<int>> matrix(N, vector<int>(N));
  int diag1 = 0;
  int diag2 = 0;
  for (int i = 0; i < N; ++i) {
    for (int j = 0; j < N; ++j) {
      cin >> matrix[i][j];
      if (i == j) {
        diag1 += matrix[i][j];
      }
      if (i + j + 1 == N) {
        diag2 += matrix[i][j];
      }

      if (j > 0) {
        matrix[i][j] += matrix[i][j - 1];
      }
    }
  }
  for (int i = 1; i < N; ++i) {
    for (int j = 0; j < N; ++j) {
      matrix[i][j] += matrix[i - 1][j];
    }
  }

  cout << (solve(N, matrix, diag1, diag2) ? "Yes" : "No") << endl;
}