added iterative CountSquareSubmatricesWithAllOnes solution (medium)

Author: minhyeong-joe

Medium/CountSquareWithOnes/README.md

@@ -0,0 +1,44 @@
+
+# Count Square Submatrices with All Ones
+[Leetcode Link](https://leetcode.com/problems/count-square-submatrices-with-all-ones/)
+
+## Problem:
+
+Given a `m * n` matrix of ones and zeros, return how many **square** submatrices have all ones.
+
+## Example:
+
+```
+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.
+```
+
+## Note:
+
+- `1 <= arr.length <= 300`
+- `1 <= arr[0].length <= 300`
+- `0 <= arr[i][j] <= 1`

Medium/CountSquareWithOnes/solution.py

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+from typing import List
+
+class Solution:
+ def countSquares(self, matrix: List[List[int]]) -> int:
+ count = 0
+ # max side length is bound by the shortest side of original matrix
+ maxSide = min(len(matrix), len(matrix[0]))
+ # print(maxSide)
+ # iterate over side length 1 to max side length, check if square is all ones (all ones if sum of elements = side**2)
+ for side in range(1, maxSide+1):
+ # print(f'======= side length of {side} ======')
+ for i in range(0, len(matrix)-side+1):
+ for j in range(0, len(matrix[i])-side+1):
+ # print(f'{i}, {j}: {matrix[i][j]}')
+ # print(f'sum of Square is: {self.sumOfSquare(matrix, i, j, side)}')
+ if self.sumOfSquare(matrix, i, j, side) == side**2:
+ count += 1
+ return count
+
+ # helper function to sum up the elements in the square given left-upper corner and side length
+ def sumOfSquare(self, matrix: List[List[int]], row: int, col: int, side: int) -> int:
+ sum = 0
+ for i in range(row, row+side):
+ for j in range(col, col+side):
+ sum += matrix[i][j]
+ return sum
+
+
+sol = Solution()
+mat = [[0,1,1,1],
+ [1,1,1,1],
+ [0,1,1,1]]
+output = sol.countSquares(mat)
+print(output)
+
+mat2 = [
+ [1,0,1],
+ [1,1,0],
+ [1,1,0]
+]
+output2 = sol.countSquares(mat2)
+print(output2)

README.md

@@ -79,6 +79,7 @@ Languages used: Java and Python
  - [Sort Colors](Medium/SortColors)
  - [Design Linked List](Medium/DesignLinkedList)
  - [Single Number II](Medium/SingleNumber2)
+ - [Count Square Submatrices with All Ones](Medium/CountSquareWithOnes)
 - Hard
  - [Maximum Score Words Formed by Letters](Hard/MaximumScoreWords)
  - [Reducing Dishes](Hard/ReducingDishes)