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
        if(head == null || head.next == null) {
            return head;
        }
        ListNode odd = head, p = odd;
        ListNode even = head.next, q = even;
        boolean flag = true;
        ListNode r = q.next;
        while(r != null) {
            if(flag) {
                p.next = r;
                p = r;
            } else {
                q.next = r;
                q = r;
            }
            r = r.next;
            flag = !flag;
        }
        q.next = null;
        p.next = even;
        return odd;
    }
}