华为机试 - 链表翻转

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链表翻转。给出一个链表和一个数k，比如链表1→2→3→4→5→6，k=2，则翻转后2→1→4→3→6→5，若k=3,翻转后3→2→1→6→5→4，若k=4，翻转后4→3→2→1→6→5，用程序实现

#include <iostream>#include <string>#include <algorithm>using namespace std;struct ListNode{int val;ListNode *link;ListNode(int v):val(v),link(NULL){ }};ListNode* reverse(ListNode *first, ListNode *second){if(first->link==second)return first;ListNode *temp=first->link;ListNode *pAhead=first->link,*pMid=pAhead->link,*pBehind=NULL;pAhead->link=second->link;while (pMid!=second){pBehind=pMid->link;pMid->link=pAhead;pAhead=pMid;pMid=pBehind;}second->link=pAhead;first->link=second;return temp;}ListNode* reverseList(ListNode *head, int k){if(k==0||k==1)return head;ListNode *leader=new ListNode(0);leader->link=head;ListNode *fisrt=leader,*second=NULL,*temp=NULL;int k_backup=k;if(k>6){second=fisrt->link;while (second!=NULL){temp=second;second=second->link;}reverse(fisrt,temp);}else{while (head!=NULL){temp=head;head=head->link;k--;if(k==1){second=head;fisrt=reverse(fisrt,second);k=k_backup;head=fisrt->link;temp=head;}}if(fisrt->link!=NULL){reverse(fisrt,temp);}}temp=leader->link;delete leader;return temp;}int main(){int n=6,k;cin>>k;ListNode *head=new ListNode(1);ListNode *temp=head;for (int i=2;i<=n;i++)temp->link=new ListNode(i),temp=temp->link;temp=reverseList(head,k);while(temp!=NULL){cout<<temp->val<<' ';temp=temp->link;}cout<<endl;system("pause");return 0;}

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