840 - Magic Squares In Grid

 JAVA

• class Solution {
      private int m;
      private int n;
      private int[][] grid;
  
      public int numMagicSquaresInside(int[][] grid) {
          m = grid.length;
          n = grid[0].length;
          this.grid = grid;
          int ans = 0;
          for (int i = 0; i < m; ++i) {
              for (int j = 0; j < n; ++j) {
                  ans += check(i, j);
              }
          }
          return ans;
      }
  
      private int check(int i, int j) {
          if (i + 3 > m || j + 3 > n) {
              return 0;
          }
          int[] cnt = new int[16];
          int[] row = new int[3];
          int[] col = new int[3];
          int a = 0, b = 0;
          for (int x = i; x < i + 3; ++x) {
              for (int y = j; y < j + 3; ++y) {
                  int v = grid[x][y];
                  if (v < 1 || v > 9 || ++cnt[v] > 1) {
                      return 0;
                  }
                  row[x - i] += v;
                  col[y - j] += v;
                  if (x - i == y - j) {
                      a += v;
                  }
                  if (x - i + y - j == 2) {
                      b += v;
                  }
              }
          }
          if (a != b) {
              return 0;
          }
          for (int k = 0; k < 3; ++k) {
              if (row[k] != a || col[k] != a) {
                  return 0;
              }
          }
          return 1;
      }
  }

C++

• class Solution {
  public:
      int numMagicSquaresInside(vector<vector<int>>& grid) {
          int m = grid.size();
          int n = grid[0].size();
          int ans = 0;
          auto check = [&](int i, int j) {
              if (i + 3 > m || j + 3 > n) {
                  return 0;
              }
              vector<int> cnt(16);
              vector<int> row(3);
              vector<int> col(3);
              int a = 0, b = 0;
              for (int x = i; x < i + 3; ++x) {
                  for (int y = j; y < j + 3; ++y) {
                      int v = grid[x][y];
                      if (v < 1 || v > 9 || ++cnt[v] > 1) {
                          return 0;
                      }
                      row[x - i] += v;
                      col[y - j] += v;
                      if (x - i == y - j) {
                          a += v;
                      }
                      if (x - i + y - j == 2) {
                          b += v;
                      }
                  }
              }
              if (a != b) {
                  return 0;
              }
              for (int k = 0; k < 3; ++k) {
                  if (row[k] != a || col[k] != a) {
                      return 0;
                  }
              }
              return 1;
          };
          for (int i = 0; i < m; ++i) {
              for (int j = 0; j < n; ++j) {
                  ans += check(i, j);
              }
          }
          return ans;
      }
  };