Maximal Square

Description:

Given a 2D binary matrix filled with 0's and 1's, find the largest square containing all 1's and return its area.

For example, given the following matrix:

1 0 1 0 0

1 0 1 1 1

1 1 1 1 1

1 0 0 1 0

Return 4.

Code:

 1  int maximalSquare(vector<vector<char>>& matrix) {

 2         int m = matrix.size();

 3         if (m==0)

 4             return 0;

 5         int n = matrix[0].size();

 6         int maxSize = 0;

 7         vector<vector<int>>d (m, vector<int>(n,0));

 8         for (int i = 0; i < n; ++i)

 9         {

10             if (matrix[0][i]=='1')

11             {

12                 d[0][i] = 1;

13                 maxSize = 1;

14             }

15         }

16         for (int j = 0; j < m; ++j)

17         {

18             if (matrix[j][0]=='1')

19             {

20                 d[j][0] = 1;

21                 maxSize = 1;

22             }

23         }

24         for (int i = 1; i < m; ++i)

25         {

26             for (int j = 1; j < n; ++j)

27             {

28                 if (matrix[i][j]=='1')

29                 {

30                     int temp = min(d[i-1][j],d[i][j-1]);

31                     d[i][j] = min(temp,d[i-1][j-1])+1;

32                     if (d[i][j] > maxSize)

33                         maxSize = d[i][j];

34                 }

35             }

36         }

37         return maxSize*maxSize;

38     }