docs: restructure problem paths, change section display to groups, and improve documentation content

apps/docs/content/(01-linear-structures)/monotonic-stack/84_largest-rectangle-in-histogram.mdx

@@ -0,0 +1,51 @@
+---
+title: '84. Largest Rectangle in Histogram'
+description: 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
+icon: dot
+topics:
+  - { name: "Array", slug: "array" }
+  - { name: "Stack", slug: "stack" }
+  - { name: "Monotonic Stack", slug: "monotonic-stack" }
+  - { name: "Range Minimum/Maximum Query", slug: "range-minimum-maximum-query" }
+issue: "https://github.com/prdlk/leetcode/issues/76"
+sidebar:
+  label: 'Largest Rectangle in Histogram'
+  badge: 'Hard'
+---
+
+### 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 <= 10^5`
+- `0 <= heights[i] <= 10^4`
+
+## Solution
+
+```py
+class Solution:
+    def largestRectangleArea(self, heights: list[int]) -> int:
+        maxArea = 0
+        stack = []
+
+        for i, h in enumerate(heights):
+            start = i
+            while stack and stack[-1][1] > h:
+                index, height = stack.pop()
+                width = i - index
+                maxArea = max(maxArea, height * width)
+                start = index
+            stack.append((start, h))
+
+        for i, h in stack:
+            maxArea = max(maxArea, h * (len(heights) - i))
+
+        return maxArea
+```