Leetcode 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 01 0 1 1 11 1 1 1 11 0 0 1 0

Return 4.

Difficulty: Medium

动态规划， 状态转移方程：matrix[i][j] = min(matrix[i-1][j-1], min(matrix[i-1][j], matrix[i][j-1])) + 1;

class Solution {public:    int maximalSquare(vector<vector<char>>& matrix) {        int row = matrix.size();        if(row == 0)            return 0;        int col = matrix[0].size();        if(col == 1 || row == 1){            for(int i = 0; i < row ;i++)                for(int j = 0; j < col; j++)                    if(matrix[i][j] == '1')                        return 1;            return 0;        }        int ans = 0;        for(int i = 0; i < row ; i++)            if(matrix[i][0] == '1')                ans = 1;        for(int i = 0; i < col ; i++)            if(matrix[0][i] == '1')                ans = 1;                for(int i = 1; i < row ; i++)            for(int j = 1; j < col; j++){                if((matrix[i][j-1] != '0' || matrix[i-1][j] != '0' || matrix[i-1][j-1] != '0') && matrix[i][j] == '1')                    matrix[i][j] = min(matrix[i-1][j-1], min(matrix[i-1][j], matrix[i][j-1])) + 1;                if(matrix[i][j] - '0' > ans)                    ans = matrix[i][j] - '0';            }        return ans * ans;                        }};