221. Maximal Square

Given a 2D binary matrix filled with 0's and 1's, find the largest square containing only 1's and return its area.For example, given the following matrix:1 0 1 0 01 0 1 1 11 1 1 1 11 0 0 1 0Return 4.

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