Count Square Submatrices with All Ones

Count Square Submatrices with All Ones

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

 

 

class Solution {
public:
    int countSquares(vector<vector<int>>& matrix) {
        int n=matrix.size(),m=matrix[0].size();
        vector<vector<int> > mat(matrix.size(),vector<int>(matrix[0].size(),0));
        int ans=0;
        for(int  i=0;i<n;++i)
        {
            for(int j=0;j<m;++j)
            {
                if(i==0||j==0)
                {
                    mat[i][j]=matrix[i][j];
                }else if(matrix[i][j]==1)
                {
                    mat[i][j]=min(mat[i-1][j-1],min(mat[i-1][j],mat[i][j-1]))+matrix[i][j];
                }else{
                    mat[i][j]=matrix[i][j];
                }
                ans=ans+mat[i][j];
            }
        }
        return ans;
       
    }
};