leetcode 221 Maximal Square

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.

Credits:

Special thanks to @Freezen for adding this problem and creating all test cases.

Subscribe to see which companies asked this question

class Solution {
public:
int maximalSquare(vector<vector<char>>& matrix) {
int n = matrix.size();
if(n == 0) return 0;
int m = matrix[0].size();
int res = 0;

vector<vector<int>> dp(n, vector<int>(m, 0));

for(int i = 0; i < n; i++) {
for(int j=0; j < m; j++) {
dp[i][j] = matrix[i][j]-'0';
if(dp[i][j] == 1) res=1;
}
}

for(int i=1; i < n; i++) {
for(int j=1; j < m; j++) {
if(matrix[i][j]=='0') continue;
dp[i][j] = min(min(dp[i-1][j], dp[i][j-1]), dp[i-1][j-1])+1;
if(dp[i][j] > res) {
res = dp[i][j];
}
}
}

return res*res;
}
};