<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 helper(int i,int j,vector<vector<int>>&matrix,vector<vector<int>>&dp,int m,int n)
    {
        if(i<0 || i>=m || j<0 || j>=n || !matrix[i][j])
        {
            return 0;
        }
        if(dp[i][j]!=-1)
        {
            return dp[i][j];
        }
        int r=helper(i,j+1,matrix,dp,m,n);
        int l=helper(i+1,j,matrix,dp,m,n);
        int d=helper(i+1,j+1,matrix,dp,m,n);

        return dp[i][j]=1+min({r,l,d});

    }
    int countSquares(vector<vector<int>>& matrix) {
        int m=matrix.size();
        int n=matrix[0].size();
        vector<vector<int>>dp(m,vector<int>(n,-1));
        int ans=0;
        for(int i=0;i<m;i++)
        {
            for(int j=0;j<n;j++)
            {
                if(matrix[i][j]==1)
                {
                    int a=helper(i,j,matrix,dp,m,n);
                    ans+=a;
                }
            }
        }
        return ans;
    }
};
30000