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

posted on 2018-04-04 10:04  lina2014  阅读(112)  评论(0编辑  收藏  举报

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