zoukankan      html  css  js  c++  java
  • Reverse Linked List

    Reverse a singly linked list.

    Thoughts:

    1.Iterative Method.

    Loop the linked list, set two pointers, one called "first" to always point to the head of the list, the other called "tail" to mark the currently looped element, each time we loop to that element, we switch the first and tail element to iteratively finish the reverse function.

    Code:

        public ListNode reverseList(ListNode head) {
            ListNode first = null;
            ListNode tail = head;
                  ListNode tmp;
            while(tail!=null){
      
            tmp=first;
            first = tail;
            tail=tail.next;
            first.next=tmp;
            }
            
            return first;
        }

    2.Recursive Method

    There's code in one reply that spells it out, but you might find it easier to start from the bottom up, by asking and answering tiny questions (this is the approach in The Little Lisper):

    1. What is the reverse of null (the empty list)? null.
    2. What is the reverse of a one element list? the element.
    3. What is the reverse of an n element list? the reverse of the second element on followed by the first element.

    Code:

    public ListNode Reverse(ListNode list)
    {
        if (list == null) return null; // first question
    
        if (list.next == null) return list; // second question
    
        // third question - in Lisp this is easy, but we don't have cons
        // so we grab the second element (which will be the last after we reverse it)
    
        ListNode secondElem = list.next;
    
        // bug fix - need to unlink list from the rest or you will get a cycle
        list.next = null;
    
        // then we reverse everything from the second element on
        ListNode reverseRest = Reverse(secondElem);
    
        // then we join the two lists
        secondElem.Next = list;
    
        return reverseRest;
    }
  • 相关阅读:
    vim删除某一列
    linux下在当前文件夹查找一个字符串信息
    .tar和.tar.gz的区别
    visual studio中调用masm汇编
    iconv转码失败的原因
    终端查看
    kubectl 常用命令总结
    Charles实战之Charles抓取https请求
    Fiddler实战之拟2G、3G、4G网络进行弱网测试
    Fiddler实战之使用Fiddler模拟弱网环境
  • 原文地址:https://www.cnblogs.com/midan/p/4656006.html
Copyright © 2011-2022 走看看