Count Square Submatrices with All Ones

Description

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(javascript)

/*
 * @lc app=leetcode id=1277 lang=javascript
 *
 * [1277] Count Square Submatrices with All Ones
 */

// @lc code=start
/**
 * @param {number[][]} matrix
 * @return {number}
 */
const countSquares = function (matrix) {
  let sum = 0
  for (let i = 0; i < matrix.length; i++) {
    for (let j = 0; j < matrix[i].length; j++) {
      if (i > 0 && j > 0 && matrix[i][j] === 1) {
        matrix[i][j] = Math.min(matrix[i - 1][j - 1], matrix[i - 1][j], matrix[i][j - 1]) + 1
      }
      sum += matrix[i][j]
    }
  }
  return sum
}
// @lc code=end