085 Maximal Rectangle 最大矩形

给定一个填充了 0 和 1 的二进制矩阵，找到最大的只包含 1 的矩形并返回其面积。
例如，给出以下矩阵：
1 0 1 0 0
1 0 1 1 1
1 1 1 1 1
1 0 0 1 0
返回 6

详见：https://leetcode.com/problems/maximal-rectangle/description/

Java实现：

class Solution {public int maximalRectangle(char[][] matrix) {if(matrix == null || matrix.length == 0 || matrix[0].length == 0){return 0;}int res = 0;int m = matrix.length;int n = matrix[0].length;int [] heights = new int[n];for(int i = 0; i<m; i++){         for(int j = 0; j<n; j++){heights[j] = matrix[i][j] == '0' ? 0 : heights[j]+1;    }res = Math.max(res, largestRectangleArea(heights));}return res;}private int largestRectangleArea(int[] heights) {int res=0;int n=heights.length;for(int i=0;i<n;++i){if(i+1<n&&heights[i]<=heights[i+1]){continue;}int minH=heights[i];for(int j=i;j>=0;--j){minH=Math.min(minH,heights[j]);int area=minH*(i-j+1);res=Math.max(res,area);}}return res;}
}

 参考：https://www.cnblogs.com/grandyang/p/4322667.html