Reverse Nodes in k-Group

Step0 / 10

Group Size (k)3

PhaseInitialize

ActionSetup

Reverse k-Group (Python)

1def reverseKGroup(head, k):
●    # Dummy node to simplify edge cases
3    dummy = ListNode(0)
......
5    prev_group_end = dummy
6 
7    while True:
......
9        group_start = prev_group_end.next
10        current = group_start
11        count = 0
......
14            current = current.next
15            count += 1
16 
......
20 
21        # Reverse the group of k nodes
22        current = group_start
......
24        for _ in range(k):
25            next_node = current.next
26            current.next = prev

Current Line (2): Dummy node creation

Reverse k-Group

Setup

Step

0 / 10

Phase

Initialize

Algorithm Progress

Group Size (k)

Phase

Initialize

Pointer Positions

Current

Group Start

Group End

None

Prev Group End

None

Algorithm Insight

Reverse nodes in groups of size k using three-pointer technique. Incomplete groups at the end stay in original order. O(n) time, O(1) space.

Press "Start" to reverse nodes in groups of size 3.

Pointer State

current1

groupStart1

groupEndNone

prevGroupEndNone

Group Size (k)

Why This Step Matters

Set k to determine group size. Each group of k nodes will be reversed.

Current Action

Initialize: k = 3, current = 1, head = 1

Explanation

Setup

Initialize Pointers

Set k = 3 to reverse nodes in groups of size 3. Start from head.

Tip

Dummy node will be used to simplify edge cases.

Phase

Setup