leetcode---Maximal Square---动规

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

Return 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 dp
[m];
int ms = 0;
for(int i=0; i<n; i++)
{
dp[i][0] = matrix[i][0] - '0';
ms = max(ms, dp[i][0]);
}
for(int j=0; j<m; j++)
{
dp[0][j] = matrix[0][j] - '0';
ms = max(ms, dp[0][j]);
}
for(int i=1; i<n; i++)
{
for(int j=1; j<m; j++)
{
if(matrix[i][j] == '1')
{
int k = min(dp[i-1][j-1], min(dp[i-1][j], dp[i][j-1]));
dp[i][j] = k + 1;
}
else
{
dp[i][j] = 0;
}
ms = max(ms, dp[i][j]);
}
}
return ms * ms;
}
};