Coding Interview Pattern 4: Recursive Call

In Merge Sort, recursion is used to divide the array into smaller parts.

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Pattern 4a — Recursive

• Merge Sort: The array is recursively divided into two halves, and then the halves are merged together in sorted order.

Common Pattern

def merge_sort(arr):
    if len(arr) > 1:
        mid = len(arr) // 2
        left = arr[:mid]
        right = arr[mid:]
        merge_sort(left)
        merge_sort(right)
        # Merge step

Pattern 4b — Dividing or Comparing Elements:

Merge Sort: Divides the array into two halves and recursively sorts them.