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 oddNode = head, evenNode = head.next, odd = oddNode, even = evenNode;
        while (odd != null || even != null) {
            if (odd != null && odd.next != null) odd.next = odd.next.next;
            if (even != null &&  even.next != null) even.next = even.next.next;
            if (odd.next == null) {
                odd.next = evenNode;
                break;
            }
            else if (odd != null) odd = odd.next;
            if (even != null) even = even.next;
        }
        return oddNode;
    }
}