LeetCode84 Largest Rectangle in Histogram java题解

题目：

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.

题解：

如果高度一致都是递增的就一直压入栈，一旦遇到一个高度减小的，就计算栈里面能够组成的最大四边形面积（一个个出栈分别计算四边形面积）

代码：

static public int largestRectangleArea(int[] height) {
		Stack stack=new Stack<>();
		int n=height.length;
		int maxarea=0;
		int i=0;
		int temp=0;
		int tempTop=0;
		while(i<=n)
		{
			temp=(i==n?0:height[i]);
			if(stack.isEmpty()||height[stack.peek()]<=temp)
			{
				stack.push(i);
				i++;
			}
			else {
				tempTop=height[stack.pop()];
				maxarea=Math.max(maxarea,tempTop*(stack.isEmpty()?i:i-1-stack.peek()) );
			}
		}

		
		 return maxarea;
		 
        
    }