#2074
Reverse Nodes in Even Length Groups
specialist · 695 · lc medium +30 · verified · 63.7% accepted · 872 likes · top 66%
Description
Given the head of a linked list, partition its nodes into consecutive groups of sizes 1, 2, 3, 4, ... (the last group may be smaller). Reverse the nodes in every even-sized group in-place, then return the modified list's head.
Example 1:
Input: head = [5,2,6,3,9,1,7,3,8,4]
Output: [5,6,2,3,9,1,4,8,3,7]
Explanation:
- The length of the first group is 1, which is odd, hence no reversal occurs.
- The length of the second group is 2, which is even, hence the nodes are reversed.
- The length of the third group is 3, which is odd, hence no reversal occurs.
- The length of the last group is 4, which is even, hence the nodes are reversed.
Example 2:
Input: head = [1,1,0,6]
Output: [1,0,1,6]
Explanation:
- The length of the first group is 1. No reversal occurs.
- The length of the second group is 2. The nodes are reversed.
- The length of the last group is 1. No reversal occurs.
Example 3:
Input: head = [1,1,0,6,5]
Output: [1,0,1,5,6]
Explanation:
- The length of the first group is 1. No reversal occurs.
- The length of the second group is 2. The nodes are reversed.
- The length of the last group is 2. The nodes are reversed.
Code
1
2
3
4
5
6
7
8