Run Continue over trapping rain water

Author: nwthomas

src/leetcode/hard/trapping-rain-water/trapping_rain_water.py

@@ -22,27 +22,44 @@
 
 
 def trap(heights: List[int]) -> int:
-    if isinstance(heights, list):
+    """
+    Compute how much water can be trapped after raining.
+
+    Args:
+        heights (List[int]): A list of non-negative integers representing an elevation map.
+
+    Returns:
+        int: The amount of water that can be trapped.
+    """
+    # Edge case: input is not a list
+    if not isinstance(heights, list):
         raise TypeError("Arguments must be of type list")
+
+    # Edge case: empty list
     if len(heights) < 1:
         return 0
 
+    # Initialize variables to keep track of water trapped and maximum heights on both sides
     water_trapped = 0
     left = 0
     right = len(heights) - 1
     max_left = heights[left]
     max_right = heights[right]
 
+    # Loop through the list until the two pointers meet
     while left < right:
+        # Move the pointer that points to the smaller maximum height
         if max_left <= max_right:
             left += 1
         else:
             right -= 1
 
+        # Update the trapped water and maximum heights for this iteration
         current_index = left if max_left <= max_right else right
         trapped = min(max_left, max_right) - heights[current_index]
         water_trapped += trapped if trapped > 0 else 0
         max_right = max(max_right, heights[right])
         max_left = max(max_left, heights[left])
 
+    # Return the total amount of water that can be trapped
     return water_trapped