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84. Largest Rectangle In Histogram

Array Stack Monotonic Stack

Problem - 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

Solutions

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class Solution:
    def largestRectangleArea(self, heights: List[int]) -> int:
        stack = []
        maxArea = 0
        heights.append(0)

        for i, h in enumerate(heights):
            while stack and h < heights[stack[-1]]:
                top = stack.pop()
                height = heights[top]
                right = i
                left = stack[-1] if stack else -1
                width = right - left - 1
                area = width*height
                maxArea = max(maxArea, area)
            stack.append(i)
        return maxArea

Submission Stats:

  • Runtime: 139 ms (92.19%)
  • Memory: 30.2 MB (68.77%)