public class Solution
extends Object
84 - Largest Rectangle in Histogram\.
Hard
Given an array of integers `heights` representing the histogram's bar height where the width of each bar is `1`, return _the area of the largest rectangle in the histogram_.
**Example 1:**
**Input:** heights = [2,1,5,6,2,3]
**Output:** 10
**Explanation:** The above is a histogram where width of each bar is 1. The largest rectangle is shown in the red area, which has an area = 10 units.
**Example 2:**
**Input:** heights = [2,4]
**Output:** 4
**Constraints:**
* 1 <= heights.length <= 105
* 0 <= heights[i] <= 104