zoukankan      html  css  js  c++  java
  • 328. Odd Even Linked List

    Given a singly linked list, group all odd nodes together followed by the even nodes. Please note here we are talking about the node number and not the value in the nodes.

    You should try to do it in place. The program should run in O(1) space complexity and O(nodes) time complexity.

    Example 1:

    Input: 1->2->3->4->5->NULL
    Output: 1->3->5->2->4->NULL
    

    Example 2:

    Input: 2->1->3->5->6->4->7->NULL
    Output: 2->3->6->7->1->5->4->NULL
    

    Note:

    • The relative order inside both the even and odd groups should remain as it was in the input.
    • The first node is considered odd, the second node even and so on ...

    two pointer

    time: O(n), space: O(1)

    /**
     * Definition for singly-linked list.
     * public class ListNode {
     *     int val;
     *     ListNode next;
     *     ListNode(int x) { val = x; }
     * }
     */
    class Solution {
        public ListNode oddEvenList(ListNode head) {
            if(head ==  null || head.next == null) {
                return head;
            }
            ListNode dummyOdd = new ListNode(0);
            ListNode dummyEven = new ListNode(0);
            ListNode curOdd = dummyOdd;
            ListNode curEven = dummyEven;
            
            ListNode cur = head;
            while(cur != null && cur.next != null) {
                curOdd.next = cur;
                curEven.next = cur.next;
                
                curOdd = curOdd.next;
                curEven = curEven.next;
                cur = cur.next.next;
            }
            if(cur != null) {
                curOdd.next = cur;
                curOdd.next.next = dummyEven.next;
            } else {
                curOdd.next = dummyEven.next;
            }
            
            curEven.next = null;
            return dummyOdd.next;
        }
    }

    optimized:

    /**
     * Definition for singly-linked list.
     * public class ListNode {
     *     int val;
     *     ListNode next;
     *     ListNode(int x) { val = x; }
     * }
     */
    class Solution {
        public ListNode oddEvenList(ListNode head) {
            if(head ==  null || head.next == null) {
                return head;
            }
            
            ListNode curOdd = head;
            ListNode evenHead = head.next;
            ListNode curEven = evenHead;
            
            while(curEven != null && curEven.next != null) {
                curOdd.next = curEven.next;
                curEven.next = curEven.next.next;
                
                curOdd = curOdd.next;
                curEven = curEven.next;
            }
            curOdd.next = evenHead;
            return head;
        }
    }
  • 相关阅读:
    Rocket broker启动失败?
    jar下载慢,maven配置国内仓库
    Linux下搭建RocketMQ环境
    几种常见css布局
    原生JS快速实现拖放
    更换 grub 主题
    安装node环境以及cnpm
    用 hexo 快速搭建博客
    关于8080端口被占用问题的解决办法。
    idea的几个常用+实用的快捷键!
  • 原文地址:https://www.cnblogs.com/fatttcat/p/10184502.html
Copyright © 2011-2022 走看看