Skip to content

750. Number Of Corner Rectangles 👍

  • Time: $O(m^2n)$
  • Space: $O(1)$
 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
class Solution {
 public:
  int countCornerRectangles(vector<vector<int>>& grid) {
    int ans = 0;

    for (int row1 = 0; row1 < grid.size() - 1; ++row1)
      for (int row2 = row1 + 1; row2 < grid.size(); ++row2) {
        int count = 0;
        for (int j = 0; j < grid[0].size(); ++j)
          if (grid[row1][j] && grid[row2][j])
            ++count;
        ans += count * (count - 1) / 2;
      }

    return ans;
  }
};

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
class Solution {
  public int countCornerRectangles(int[][] grid) {
    int ans = 0;

    for (int row1 = 0; row1 < grid.length - 1; ++row1)
      for (int row2 = row1 + 1; row2 < grid.length; ++row2) {
        int count = 0;
        for (int j = 0; j < grid[0].length; ++j)
          if (grid[row1][j] == 1 && grid[row2][j] == 1)
            ++count;
        ans += count * (count - 1) / 2;
      }

    return ans;
  }
}