题解 | 链表的奇偶重排

import java.util.*;

/*
 * public class ListNode {
 *   int val;
 *   ListNode next = null;
 *   public ListNode(int val) {
 *     this.val = val;
 *   }
 * }
 */

public class Solution {
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     * 
     * @param head ListNode类 
     * @return ListNode类
     */
    public ListNode oddEvenList (ListNode head) {
        // write code here

        ListNode oddHead = new ListNode(-1);
        ListNode oddTail = oddHead;

        ListNode evenHead = new ListNode(-1);
        ListNode evenTail = evenHead;

        int i = 1;
        while(head != null) {
            if (i % 2 != 0) {
                oddTail.next = new ListNode(head.val);
                oddTail = oddTail.next;

            } else {
                evenTail.next = new ListNode(head.val);
                evenTail = evenTail.next;

            }
            i++;
            head = head.next;
        }
        oddTail.next = evenHead.next;
        return oddHead.next;
    }
}

1、遍历，产生2条链；

2、组合；

3、去头；