[LeetCode] largest Rectangle In Histogram

Largest Rectangle in Histogram

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.



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



The largest rectangle is shown in the shaded area, which has area = 10 unit.

For example,

Given height = [2,1,5,6,2,3],

return 10.

思路：假设第n个柱形高度即为最大直方图的高，左右两个指针，分别代表直方图的最左侧位置和最右侧位置。那么，最大面积 area= （right-left+1）*h

package leetcode.largestRectangleInHistogram;

public class LargestRectangleHistogram {

public static void main(String[] args) {
int[] heights={2,1,5,6,2,3};
int max=0;
for(int i=0;i<heights.length;i++){
int left=i;
int right=i;
while(--left>=0){
if (heights[left]<heights[i]) {

break;
}
}

while(++right<heights.length){
if (heights[right]<heights[i]) {
break;
}
}
int area=(--right-++left+1)* heights[i];
max=area>max?area:max;
System.out.println(max);

}

}

}