221. Maximal Square(动态规划)

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

Example:

Input: 

1 0 1 0 0
1 0 1 1 1
1 1 1 1 1
1 0 0 1 0

Output: 4

dp[i][j] =  min(dp[i-1][j-1],min(dp[i-1][j],dp[i][j-1]))+1;

class Solution {
public:
    int maximalSquare(vector<vector<char>>& matrix) {
        int n = matrix.size();
        if(n==0) return 0;
        int m = matrix[0].size();
        vector<vector<int> > dp(n+1,vector<int>(m+1,0));
        int res =0;
        for(int i = 1;i <=n;i++)
            for(int j = 1;j<=m;j++){

                if(matrix[i-1][j-1]=='1')
                    dp[i][j] =  min(dp[i-1][j-1],min(dp[i-1][j],dp[i][j-1]))+1;
                    res  = max(res,dp[i][j]);
                }
         
        return res*res;
    }
    
};