<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>

class Solution {
public:
    int dp[500][500];
    int method(int i,int j, vector<vector<int>>&matrix, int m, int n)
    {
        if(i>=m || j>=n || matrix[i][j]==0||i<0||j<0)
         return 0;
        if(dp[i][j]!=-1)
           return dp[i][j];
        //right
        int right = method(i,j+1,matrix,m,n);
        //down
        int down = method(i+1,j,matrix,m,n);
        //bottom right
        int br = method(i+1,j+1,matrix,m,n);
        return dp[i][j]=1 + min({down, right, br});
    }
    int countSquares(vector<vector<int>>& matrix) {
        int ans =0;
        memset(dp,-1,sizeof(dp));
        for(int i=0;i<matrix.size();i++)
        {
            for(int j=0;j<matrix[0].size();j++)
            {
                if(matrix[i][j]==1)
                   ans+=method(i,j,matrix,matrix.size(), matrix[0].size());
            }
        }
        return ans;
    }
};
28500