2.2.13—单链表—Reorder List

描述
Given a singly linked listL0 L1 ...Ln;reorder it to:L0 Ln L1 Ln-1...
You must do this in-place without altering the nodes values.
For example, Given [1,2,3,4], reorder it to [1,4,2,3].

#include<iostream>using namespace std;struct node{int data;node *next;};class mylist{node *head;public:mylist(){head = new node();head->next = NULL;}void CreateList(int a[], int n);void Display();friend void ReorderList(mylist &list);~mylist();};void mylist::CreateList(int a[], int n){node *p = head;node *temp = head;for (int i = 0; i < n; i++){node *q = new node();q->data = a[i];p->next = q;p = q;}p->next = NULL;}void mylist::Display(){node *p = head->next;while (p){cout << p->data << " ";p = p->next;}cout << endl;}void ReorderList(mylist &list){int length = 0;node *p = list.head->next;while (p){length++;p = p->next;}//===int lasthalf = length / 2;int firsthalf = length - lasthalf;p = list.head->next;node *firsthalfend = list.head;node *lasthalfbegin = NULL;for (int i = 1; i <= firsthalf; i++){firsthalfend = firsthalfend->next;}lasthalfbegin = firsthalfend->next;firsthalfend->next = NULL;//===list.head->next = NULL;while (lasthalfbegin){node *temp = lasthalfbegin->next;lasthalfbegin->next = list.head->next;list.head->next = lasthalfbegin;lasthalfbegin = temp;}lasthalfbegin = list.head->next;list.head->next = p;//===while (p&&lasthalfbegin){node *temp1 = p;node *temp2 = lasthalfbegin;p = p->next;lasthalfbegin = lasthalfbegin->next;temp1->next = temp2;temp2->next = p;}}mylist::~mylist(){node *p = head;while (p){node *temp = p->next;delete p;p = temp;}}int main(){//===const int n = 4;int a[n] = { 1, 2, 3, 4};mylist list;list.CreateList(a, n);list.Display();cout << endl;//===ReorderList(list);list.Display();cout << endl;}