LeetCode/1277_Count_Square_Submatrices_with_All_Ones.py at main · AnmolPatel20/LeetCode · GitHub

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"""
Given a m * n matrix of ones and zeros, return how many square submatrices have all ones.


Example 1:

Input: matrix =
[
  [0,1,1,1],
  [1,1,1,1],
  [0,1,1,1]
]
Output: 15
Explanation:
There are 10 squares of side 1.
There are 4 squares of side 2.
There is  1 square of side 3.
Total number of squares = 10 + 4 + 1 = 15.
Example 2:

Input: matrix =
[
  [1,0,1],
  [1,1,0],
  [1,1,0]
]
Output: 7
Explanation:
There are 6 squares of side 1.
There is 1 square of side 2.
Total number of squares = 6 + 1 = 7.


Constraints:

1 <= arr.length <= 300
1 <= arr[0].length <= 300
0 <= arr[i][j] <= 1
"""

class Solution:
    def countSquares(self, matrix: List[List[int]]) -> int:
        row, col = len(matrix), len(matrix[0])
        dp = [[0] * (col + 1) for _ in range(row + 1)]
        ans = 0
        for i in range(row):
            for j in range(col):
                if matrix[i][j]:
                    dp[i + 1][j + 1] = (
                        min(dp[i][j + 1], dp[i + 1][j], dp[i][j]) + 1
                    )
                    ans += dp[i + 1][j + 1]
        return ans