1277. Count Square Submatrices with All Ones

 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

Solution:

	class Solution(object):
	def countSquares(self, matrix):
	"""
	:type matrix: List[List[int]]
	:rtype: int
	"""
	m,n = len(matrix),len(matrix[0])
	for i in range(1,m):
	for j in range(1,n):
	if matrix[i][j]==1:
	matrix[i][j] = 1+min([matrix[i][j-1],matrix[i-1][j],matrix[i-1][j-1]])
	s = 0
	for i in range(m):
	for j in range(n):
	s+=matrix[i][j]
	return s

view raw count-square-submatrices-with-all-ones.py hosted with ❤ by GitHub