Leetcode•Oct 27, 2026

Count Square Submatrices with All Ones

Hazrat Ali

Leetcode

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.

Solution
var countSquares = function(matrix) {
    const m = matrix.length;
    const n = matrix[0].length;

    const dp = Array.from({ length: m }, () => Array(n).fill(0));
    let count = 0;

    for (let i = 0; i < m; i++) {
        for (let j = 0; j < n; j++) {
            if (matrix[i][j] === 1) {
                if (i === 0 || j === 0) {
                    dp[i][j] = 1;
                } else {
                    dp[i][j] = 1 + Math.min(
                        dp[i - 1][j],
                        dp[i][j - 1],
                        dp[i - 1][j - 1]
                    );
                }

                count += dp[i][j];
            }
        }
    }

    return count;
};


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