Refactor docstring and type hints in merge_intervals

Updated type hints and docstring formatting in merge_intervals function.

Author: gokul000410

data_structures/arrays/merge_intervals.py

@@ -1,25 +1,24 @@
 def merge_intervals(intervals: list[list[int]]) -> list[list[int]]:
-    """
+   """
     Merge all overlapping intervals.
 
     Each interval is represented as a list of two integers [start, end].
     The function merges overlapping intervals and returns a list of
     non-overlapping intervals sorted by start time.
 
     Parameters:
-    intervals (List[List[int]]): A list of intervals.
+    intervals (list[list[int]]): A list of intervals.
 
     Returns:
-    List[List[int]]: A list of merged non-overlapping intervals.
+    list[list[int]]: A list of merged non-overlapping intervals.
 
-      Edge Cases Handled:
+    Edge Cases Handled:
     - Empty list: returns []
     - Single interval: returns the interval itself
     - Intervals already sorted or unsorted
     - Fully overlapping intervals
     - Invalid intervals (e.g., [[]] or intervals not having exactly 2 integers) raise ValueError
 
-
     Examples:
     >>> merge_intervals([[1, 3], [2, 6], [8, 10], [15, 18]])
     [[1, 6], [8, 10], [15, 18]]
@@ -33,19 +32,18 @@ def merge_intervals(intervals: list[list[int]]) -> list[list[int]]:
     [[1, 4]]
 
     Time Complexity:
-    O(n log n) – sorting the intervals, where n is the number of intervals.
+    O(n log n) - sorting the intervals, where n is the number of intervals.
 
     Space Complexity:
-    O(n) – storing the merged intervals.
+    O(n) - storing the merged intervals.
     """
 
     if not intervals:
         return []
     for interval in intervals:
+        msg = f"Each interval must have exactly 2 integers, got {interval}"
         if len(interval) != 2:
-            raise ValueError(
-                f"Each interval must have exactly 2 integers, got {interval}"
-            )
+            raise ValueError(msg)
     # Sort intervals based on the start time
     intervals.sort(key=lambda interval: interval[0])