largest-rectangle-in-histogram[最大矩形]

题目描述

Given n non-negative integers representing the histogram's bar height where the width of each bar is 1, find the area of largest rectangle in the histogram.

image1

Above is a histogram where width of each bar is 1, given height =[2,1,5,6,2,3].

image2

The largest rectangle is shown in the shaded area, which has area =10unit.
For example,
Given height =[2,1,5,6,2,3],
return 10.

• 思路
  对每个柱形遍历，每次找其左边连续比它大或相等的，右边同理。最后求其最大值即可。

public class Solution {
    public int largestRectangleArea(int[] height) {
        if(height == null || height.length == 0)
            return 0;
        
        int ans = 0;
        for(int i=0; i=0; j--){
                if(height[j] >= val)
                    cntL ++;
                else
                    break;
            }
            int cntR = 0;
            for(int j=i+1; j= val)
                    cntR ++;
                else
                    break;
            }
            
            ans = Math.max(ans, height[i] * (cntL + cntR + 1));
        }
        return ans;
    }
}