Largest Rectangle in Histogram

Given an array of integers heights representing the histogram's bar heights where the width of each bar is 1, return the area of the largest rectangle in the histogram.

A rectangle must be contained entirely within the histogram - it cannot extend above any bar it spans.

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Example 1

       #
     # #
     # #
     # #   #
 #   # # # #
 # # # # # #
 2 1 5 6 2 3

Input: heights = [2, 1, 5, 6, 2, 3]
Output: 10
Explanation: The largest rectangle spans bars at index 2 and 3 (heights 5 and 6), giving area = min(5,6) * 2 = 10.

Example 2

Input: heights = [2, 4]
Output: 4
Explanation: The largest rectangle is the single bar of height 4, giving area = 4 * 1 = 4.

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Constraints

• 1 <= heights.length <= 10^5
• 0 <= heights[i] <= 10^4