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;
        }

        List<ListNode> jsList = new ArrayList<>();
        List<ListNode> osList = new ArrayList<>();

        ListNode jsNode = head;
        ListNode osNode = head.next;

        //奇数节点入List
        while (jsNode != null) {
            jsList.add(jsNode);
            jsNode = jsNode.next;
            if(jsNode != null){
                jsNode = jsNode.next;
            }
        }
        
        //偶数节点入List
        while (osNode != null) {
            osList.add(osNode);        
            osNode = osNode.next;
            if(osNode != null){
                osNode = osNode.next;
            }
        }
        
        //定义虚拟节点
        ListNode newHeadNode = new ListNode(-1);
        ListNode tempHead = newHeadNode;
        for (int i = 0; i < jsList.size(); i++) {
            newHeadNode.next = jsList.get(i);
            newHeadNode = newHeadNode.next;
        }

        for (int i = 0; i < osList.size(); i++) {
            newHeadNode.next = osList.get(i);
            newHeadNode = newHeadNode.next;
        }
        //newHeadNode.next = null 防止产生环
        newHeadNode.next = null;
        return tempHead.next;

    }
}