Solution.cs

namespace LeetCodeNet.G0001_0100.S0084_largest_rectangle_in_histogram {

// #Hard #Top_100_Liked_Questions #Top_Interview_Questions #Array #Stack #Monotonic_Stack
// #Big_O_Time_O(n_log_n)_Space_O(log_n) #2024_01_08_Time_304_ms_(30.92%)_Space_52.4_MB_(29.92%)

public class Solution {
    public int LargestRectangleArea(int[] heights) {
        int maxArea = 0, i = 0;
        Stack<int> stack = new Stack<int>();
        while (i <= heights.Length) {
            var currHeight = i == heights.Length ? 0 : heights[i];
            if (!stack.Any() || currHeight >= heights[stack.Peek()]) {
                stack.Push(i);
                i++;
            }
            else {
                int index = stack.Pop();
                int height = heights[index];
                int width = (!stack.Any()) ? i : (i - 1) - stack.Peek();
                maxArea = Math.Max(maxArea, height * width);
            }
        }
        return maxArea;
    }
}
}