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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 <= 1050 <= heights[i] <= 104
Solution
# @param {Integer[]} heights
# @return {Integer}
def largest_rectangle_area(heights)
area = 0
stack = []
return 0 if heights.empty?
return heights[0] * heights.length if heights.uniq.length == 1
heights.each.with_index do |height, index|
start = index
while !stack.empty? && stack.last[1] > height do
i, h = stack.pop
area = [area, h * (index - i)].max
start = i
end
stack << [start, height]
end
stack.each do |i, s|
area = [area, s * (heights.length - i)].max
end
area
end