Problem
Given a m * n matrix of ones and zeros, return how many square submatrices have all ones.Examples
Constraints
- 1 <= arr.length <= 300
- 1 <= arr[0].length <= 300
- 0 <= arr[i][j] <= 1
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Tested Python solution for LeetCode 1277 with 15 pytest cases. Generate a practice environment with lcpy.
lcpy gen -n 1277 # by problem number
lcpy gen -s count_square_submatrices_with_all_ones # by problem name
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.
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.
class Solution:
def count_squares(self, matrix: list[list[int]]) -> int:
m, n = len(matrix), len(matrix[0])
total = 0
for i in range(m):
for j in range(n):
if matrix[i][j] and i > 0 and j > 0:
matrix[i][j] = 1 + min(matrix[i - 1][j], matrix[i][j - 1], matrix[i - 1][j - 1])
total += matrix[i][j]
return total
| Time | Space |
|---|---|
| - | - |