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K-way Merge Sort

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K-way Merge Sort

Don’t start K-way Merge Sort with jargon. Start with names A→Z. That is the whole point.

Do K-way Merge Sort once by hand. n log n vs n². Change one input. Say the new result out loud.

Without K-way Merge Sort, the roll list gets messy and names A→Z is hard to trust.

K-way Merge Sort shows up in the roll list. Name names A→Z, not “a real-world scenario”.

If names A→Z breaks under K-way Merge Sort, check unstable sort when equal keys matter first.

Place K-way Merge Sort next to nearby DSA work — n log n vs n² is the link.

Viva for K-way Merge Sort — what it is → n log n vs n² → the mistake (unstable sort when equal keys matter).

Exam tip

Say K-way Merge Sort in one breath, then n log n vs n², then unstable sort when equal keys matter.

Example

def merge_sort(arr):
    if len(arr) <= 1:
        return arr
    mid = len(arr) // 2
    left = merge_sort(arr[:mid])
    right = merge_sort(arr[mid:])
    out, i, j = [], 0, 0
    while i < len(left) and j < len(right):
        if left[i] <= right[j]:
            out.append(left[i]); i += 1
        else:
            out.append(right[j]); j += 1
    return out + left[i:] + right[j:]

print(merge_sort([5, 1, 4, 2]))

K-way Merge Sort — merge sort divides the array, sorts halves, then merges — O(n log n).

Short notes

DefK-way Merge Sort — Vikram uses it for names A→Z in the roll list.
RuleK-way Merge Sort → n log n vs n².
RememberK-way Merge Sort + time vs memory (the roll list).
UseK-way Merge Sort in the roll list (names A→Z).
TrapK-way Merge Sort — unstable sort when equal keys matter.
ExK-way Merge Sort → names A→Z.

def merge_sort(arr): if len(arr) <= 1: return arr mid = len(arr) // 2 left = merge_sort(arr[:mid]) right = merge_sort(arr[mid:]) out, i, j = [], 0, 0 while i < len(left) and j < len(right): if left[i] <= right[j]: out.append(left[i]); i += 1 else: out.append(right[j]); j += 1 return out + left[i:] + right[j:] print(merge_sort([5, 1, 4, 2]))

K-way Merge Sort

Example

Short notes

Questions

K-way Merge Sort

Example

Short notes

Questions