DSA · Theory

Merge Sort on Doubly Linked List

← All stacks

Theory

196/810

Merge Sort on Doubly Linked List

Merge Sort on Doubly Linked List is simple if you keep it on paper. Sara uses it for a ticket queue node in a counter.

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

Merge Sort on Doubly Linked List exists so Sara can keep a ticket queue node correct in a counter.

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

Merge Sort on Doubly Linked List miss — losing the next pointer on delete. Fix it before you talk about advanced DSA.

Merge Sort on Doubly Linked List is not a lonely heading. Sara ties it to a ticket queue node.

Close Merge Sort on Doubly Linked List with: “If I skip it, a ticket queue node goes wrong like this: losing the next pointer on delete.”

Diagram

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

Exam tip

For Merge Sort on Doubly Linked List: definition + a counter + one failure.

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 Doubly Linked List — merge sort divides the array, sorts halves, then merges — O(n log n).

Short notes

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

Example

Short notes

Questions

Merge Sort on Doubly Linked List

Example

Short notes

Questions