750

Given a grid where each entry is only 0 or 1, find the number of corner rectangles.

A corner rectangle is 4 distinct 1s on the grid that form an axis-aligned rectangle. Note that only the corners need to have the value 1. Also, all four 1s 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.

 

Example 3:

Input: grid = [[1, 1, 1, 1]] Output: 0 Explanation: Rectangles must have four distinct corners.

 

 

먼저 Counter() 이건 Key, Value로 세주는것이다

 

enumerate를 통해 index 와 값을 가지고있는다. 

 

그리고 <----> 이런 length의 counter를 가지고있으면 된다. 

 

그걸 count[c1,c2] 로 가지고있으면 됩니다. 

 

 

return ans

 

DP는 아니네