diff --git a/data_structures/stacks/largest_rectangle_histogram.py b/data_structures/stacks/largest_rectangle_histogram.py new file mode 100644 index 000000000..107fb41c4 --- /dev/null +++ b/data_structures/stacks/largest_rectangle_histogram.py @@ -0,0 +1,39 @@ +def largest_rectangle_area(heights: list[int]) -> int: + """ + Given an array of integers representing the heights of bars, + this function returns the area of the largest rectangle that can be formed + + >>> largest_rectangle_area([2, 1, 5, 6, 2, 3]) + 10 + + >>> largest_rectangle_area([2, 4]) + 4 + + >>> largest_rectangle_area([6, 2, 5, 4, 5, 1, 6]) + 12 + + >>> largest_rectangle_area([1]) + 1 + """ + stack: list[int] = [] + max_area = 0 + heights = [*heights, 0] # make a new list by appending the sentinel 0 + n = len(heights) + + for i in range(n): + # make sure the stack remains in increasing order + while stack and heights[i] < heights[stack[-1]]: + h = heights[stack.pop()] # height of the bar + # if stack is empty, it means entire width can be taken from index 0 to i-1 + w = i if not stack else i - stack[-1] - 1 # calculate width + max_area = max(max_area, h * w) + + stack.append(i) + + return max_area + + +if __name__ == "__main__": + import doctest + + doctest.testmod()