Leetcode-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.

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Solution:

public class Solution {
    public int largestRectangleArea(int[] height) {
        if (height.length==0) return 0;

        Stack<Integer> index = new Stack<Integer>();
        index.push(-1);
        int max = 0;
        for (int i=0;i<height.length;i++){
            while (index.peek()!=-1){
                if (height[index.peek()]>height[i]){
                    int cur = index.pop();
                    max = Math.max(max,height[cur]*(i-index.peek()-1));
                } else break;
            }
            index.push(i);
        }

        while (index.peek()!=-1){
            int cur = index.pop();
            max = Math.max(max,height[cur]*(height.length-index.peek()-1));
        }

        return max;
    }    
       
}