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) {
        ListNode head1 = new ListNode(-1);
        ListNode head2 = new ListNode(-1);
        ListNode index1 = head1;
        ListNode index2 = head2;
        int index = 1;
        while(head != null) {
            if (index % 2 != 0) {
                index1.next = head;
                head = head.next;
                index1 = index1.next;
                index1.next = null;
            } else {
                index2.next = head;
                head = head.next;
                index2 = index2.next;
                index2.next = null;
            }
            index++;
        }

        index1.next = head2.next; 
        head = head1.next;
        return head;
    }
}