328. Odd Even Linked List

题目

原始地址：https://leetcode.com/problems/odd-even-linked-list/#/description

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) { val = x; }
 * }
 */
public class Solution {
    public ListNode oddEvenList(ListNode head) {
        
    }
}

描述

给定一个单链表，要求把所有奇数节点和偶数节点分开，并且奇数节点在前偶数节点在后，按照原来的相对顺序返回。

分析

题目很简单，新建两个链表头oddHead和evenHead，然后依次把节点分别放入即可。注意最后要把even的next置为null，否则可能会出现环的情况。

解法

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) { val = x; }
 * }
 */
public class Solution {
    public ListNode oddEvenList(ListNode head) {
        ListNode oddHead = new ListNode(0), odd = oddHead, evenHead = new ListNode(0), even = evenHead, curr = head;
        while(curr != null){
            if(curr != odd.next){
                odd.next = curr;
                odd = odd.next;
            } else {
                even.next = curr;
                even = even.next;
            }
            curr = curr.next;
        }
        odd.next = evenHead.next;
        even.next = null;
        return oddHead.next;
    }
}