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) return head;
        ListNode dummy = new ListNode(-1);
        int i = 0;
        ListNode last = head;
        ListNode cur = head;
        ListNode dual = dummy;
        while (cur != null) {
            if ( i % 2 == 0 ) {
                last = cur;
                i++;
                cur = cur.next;
            } else {
                dual.next = cur;
                last.next = cur.next;
                cur.next = null;
                i++;
                cur = last.next;
                dual = dual.next;
            }
        }
        last.next = dummy.next;
        return head;
    }
}