655. Number Of Corner Rectangles
Given an m x n integer matrix grid where each entry is only 0 or 1, return the number of corner rectangles.
A corner rectangle is four distinct 1's on the grid that forms an axis-aligned rectangle. Note that only the corners need to have the value 1. Also, all four 1's used must be distinct.
Example 1:
Input: grid = [[1,0,0,1,0],[0,0,1,0,1],[0,0,0,1,0],[1,0,1,0,1]]
Output: 1
Explanation: There is only one corner rectangle, with corners grid[1][2], grid[1][4], grid[3][2], grid[3][4].
Example 2:
Input: grid = [[1,1,1],[1,1,1],[1,1,1]]
Output: 9
Explanation: There are four 2x2 rectangles, four 2x3 and 3x2 rectangles, and one 3x3 rectangle.
Now Your Turn!
Pick the correct output for the given inputInput: grid = [[1,0,1],[1,0,1],[1,0,1]]
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Constraints:
- m == grid.length
- n == grid[i].length
- 1 <= m, n <= 200
- grid[i][j] is either 0 or 1.
- The number of 1's in the grid is in the range [1, 6000].