LeetCode：85. Maximal Rectangle（最大的矩形）

Given a 2D binary matrix filled with 0's and 1's, find the largest rectangle containing only 1's and return its area.

Example:

Input:
[
  ["1","0","1","0","0"],
  ["1","0","1","1","1"],
  ["1","1","1","1","1"],
  ["1","0","0","1","0"]
]
Output: 6

---

方法1：

class Solution {
    public int maximalRectangle(char[][] matrix) {
        if(matrix==null || matrix.length==0)
            return 0;
        int res = 0;
        int m = matrix.length;
        int n = matrix[0].length;
        int[] left = new int[n];
        int[] right = new int[n];
        int[] height = new int[n];
        Arrays.fill(right,n);
        for(int i = 0; i<m; i++){
            int curleft = 0, curright = n;
            for(int j = 0; j<n;j++){
                if(matrix[i][j]=='1')
                    height[j]++;
                else
                    height[j] = 0;
            }
            for(int j = 0;j<n; j++){
                if(matrix[i][j]=='1'){
                    left[j]=Math.max(left[j],curleft);
                }else{
                    left[j]=0;
                    curleft = j+1;
                }
            }
            for(int j = n-1;j>=0;j--){
                if(matrix[i][j]=='1')
                    right[j] = Math.min(right[j],curright);
                else{
                    right[j] = n;
                    curright = j;
                }
            }
            for(int j = 0; j<n;j++){
                res = Math.max(res,(right[j]-left[j])*height[j]);
            }
        }
        return res;
        
    }
}

时间复杂度：O(n^3)

空间复杂度：O(n)

---

源码github地址：https://github.com/zhangyu345293721/leetcode