Untitled

class Solution {
public:
    int maximalSquare(vector<vector<char>>& mat) {
        if(mat.empty()) return 0;
        int r=mat.size(),c =mat[0].size();
        int sz=0;
        vector<vector<int>> dp(r,vector<int>(c,0));

        for(int i=0;i<r;i++){
            for(int j=0;j<c;j++){
                if(!i || !j || mat[i][j]=='0') dp[i][j]=mat[i][j]-'0'; // store 0, cant form square
                else{
                    dp[i][j]=1 + min(dp[i-1][j],min(dp[i-1][j-1],dp[i][j-1]));
                }
                sz=max(sz,dp[i][j]);
            }
        }
        return sz*sz;
        
    }
};