ListNode Review Reverselistnode

1. Reverse Linked List

Iterative:core Code

if NULL NULL )     return= null;    while NULL ) {     = current.next;      = head;      = current ;     = Temp.next;} return head;

Recurring:core Code

    Public ListNode reverselist (ListNode head) {         if (head = = NULL | | head.next = = NULL)            return head;         ListNode second = Head.next;         Head.next = null;         ListNode res =  reverselist (second);         Second.next  = head;         return res;    }

　　

Reverse Linked List II

Reverse a linked list from position m to N. Do it in-place and in One-pass.

For example:
Given 1->2->3->4->5->NULL , m = 2 and n = 4,

Return 1->4->3->2->5->NULL .

Note:
Given m, n satisfy the following condition:
1 ≤ m ≤ n ≤length of list.

Point:reverse

/** * Definition for singly-linked list. * public class ListNode {*     int val; *     ListNode Next; *     listnode (int x) {val = x;}}} */public class Soluti On {public    ListNode Reversebetween (listnode head, int m, int n) {        if (head = = NULL | | head.next = = NULL)            retur n Head;        ListNode res = new ListNode ( -1);        Res.next = head;        ListNode pre = res;        for (int i = 0; i < m-1; i + +) {            pre = Pre.next;        }        ListNode first = Pre.next;        ListNode second = First.next;        for (int i = 0; i < n-m; i++) {            first.next = Second.next;            Second.next = Pre.next;            Pre.next = second;            second = First.next;        }        return res.next;    }    }

　　

　　

ListNode Review Reverselistnode