DSA · Theory

Merge Sort on Singly Linked Lists

Theory

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Merge Sort on Singly Linked Lists

Merge Sort on Singly Linked Lists is simple if you keep it on paper. Meera uses it for a ticket queue node in a counter.

Merge Sort on Singly Linked Lists on the board: head → next → …. Then say what a ticket queue node looks like after.

Merge Sort on Singly Linked Lists exists so Meera can keep a ticket queue node correct in a counter.

Merge Sort on Singly Linked Lists shows up in a counter. Name a ticket queue node, not “a real-world scenario”.

Merge Sort on Singly Linked Lists trap — losing the next pointer on delete. Meera loses marks for that every viva.

After Merge Sort on Singly Linked Lists, Meera should still remember losing the next pointer on delete.

One breath for Merge Sort on Singly Linked Lists, then a ticket queue node, then losing the next pointer on delete. Sit down.

Diagram

  [10] → [20] → [30] → /
   head              tail

Exam tip

Say Merge Sort on Singly Linked Lists in one breath, then head → next → …, then losing the next pointer on delete.

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]))

Merge Sort on Singly Linked Lists — merge sort divides the array, sorts halves, then merges — O(n log n).

Short notes

DefMerge Sort on Singly Linked Lists — Meera uses it for a ticket queue node in a counter.
RuleMerge Sort on Singly Linked Lists → head → next → ….
RememberMerge Sort on Singly Linked Lists + Big-O (a counter).
UseMerge Sort on Singly Linked Lists in a counter (a ticket queue node).
TrapMerge Sort on Singly Linked Lists — losing the next pointer on delete.
ExMerge Sort on Singly Linked Lists → a ticket queue node.

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]))

Merge Sort on Singly Linked Lists

Example

Short notes

Questions

Merge Sort on Singly Linked Lists

Example

Short notes

Questions