[leetcode] Maximal Square

Problem:

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:

Return 4.

比较详细的解法在这里:

https://leetcode.com/discuss/38489/easy-solution-with-detailed-explanations-8ms-time-and-space

附上最终的代码:

 1 int maximalSquare(vector<vector<char>>& matrix) 
 2 {
 3     if (matrix.empty()) return 0;
 4     int m = matrix.size(), n = matrix[0].size();
 5     vector<int> dp(m + 1, 0);
 6     int maxsize = 0, pre = 0;
 7     for (int j = 0; j < n; j++) {
 8         for (int i = 1; i <= m; i++) {
 9             int temp = dp[i];
10             if (matrix[i - 1][j] == '1') {
11                 dp[i] = min(dp[i], min(dp[i - 1], pre)) + 1;
12                 maxsize = max(maxsize, dp[i]);
13             }
14             else dp[i] = 0;
15             pre = temp;
16         }
17     }
18     return maxsize * maxsize;
19 }