LeetCode:Reverse LinkedListⅡ
Problem:
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.
Solution:逆转用的头插法
/** * Definition for singly-linked list. * struct ListNode { * int val; * ListNode *next; * ListNode(int x) : val(x), next(NULL) {} * }; */ class Solution { public: ListNode* reverseBetween(ListNode* head, int m, int n) { ListNode result(-1); result.next=head; ListNode *prev=&result; for(int i=0;i<m-1;i++) prev=prev->next; ListNode *head2=prev; prev=head2->next; ListNode *cur=prev->next; for(int i=m;i<n;i++) { prev->next=cur->next; cur->next=head2->next; head2->next=cur; //头插法 cur=prev->next; } return result.next; } };