Count Square Submatrices with All Ones
<p>Given a <code>m * n</code> matrix of ones and zeros, return how many <strong>square</strong> submatrices have all ones.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>

<pre>
<strong>Input:</strong> matrix =
[
&nbsp; [0,1,1,1],
&nbsp; [1,1,1,1],
&nbsp; [0,1,1,1]
]
<strong>Output:</strong> 15
<strong>Explanation:</strong> 
There are <strong>10</strong> squares of side 1.
There are <strong>4</strong> squares of side 2.
There is  <strong>1</strong> square of side 3.
Total number of squares = 10 + 4 + 1 = <strong>15</strong>.
</pre>

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> matrix = 
[
  [1,0,1],
  [1,1,0],
  [1,1,0]
]
<strong>Output:</strong> 7
<strong>Explanation:</strong> 
There are <b>6</b> squares of side 1.  
There is <strong>1</strong> square of side 2. 
Total number of squares = 6 + 1 = <b>7</b>.
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>1 &lt;= arr.length&nbsp;&lt;= 300</code></li>
	<li><code>1 &lt;= arr[0].length&nbsp;&lt;= 300</code></li>
	<li><code>0 &lt;= arr[i][j] &lt;= 1</code></li>
</ul>
Array; Dynamic Programming; Matrix
function countSquares(matrix: number[][]): number {
    const [m, n] = [matrix.length, matrix[0].length];
    const f = Array.from({ length: m }, () => Array(n));
    const dfs = (i: number, j: number): number => {
        if (i === m || j === n || !matrix[i][j]) return 0;
        f[i][j] ??= 1 + Math.min(dfs(i + 1, j), dfs(i, j + 1), dfs(i + 1, j + 1));
        return f[i][j];
    };
    let ans = 0;

    for (let i = 0; i < m; i++) {
        for (let j = 0; j < n; j++) {
            ans += dfs(i, j);
        }
    }

    return ans;
}
