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143.cpp
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143.cpp
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#include <iostream>
using namespace std;
// Definition for singly-linked list.
struct ListNode {
int val;
ListNode *next;
ListNode(int x) : val(x), next(NULL) {}
};
class Solution {
public:
ListNode * reserve(ListNode *head)
{
ListNode *newhead=head;
head=head->next;
newhead->next=NULL;
ListNode *temp;
while(head)
{
temp=head->next;
head->next=newhead;
newhead=head;
head=temp;
}
return newhead;
}
void reorderList(ListNode* head) {
ListNode *cur=head;
int sum=0;
while(cur)
{
++sum;
cur=cur->next;
}
if(sum<=2)
return ;
if(sum%2==0)
sum=sum/2;
else
sum=sum/2+1;
int count=0;
cur=head;
while(cur)
{
++count;
if(count>sum)
break;
cur=cur->next;
}
ListNode *start2=reserve(cur);
ListNode *start1=head;
while(start1)
{
if(start1->next==cur)
start1->next=NULL;
start1=start1->next;
}
start1=head;
ListNode *temp1;
ListNode *temp2;
while(start1&&start2)
{
temp1=start1->next;
// cout<<"123 "<<temp1->val<<endl;
start1->next=start2;
// cout<<"123 "<<start1->next->val<<endl;
temp2=start2->next;
// cout<<"123 "<<temp2->val<<endl;
start2->next=temp1;
// cout<<"123 "<<start2->next->val<<endl;
start1=temp1;
// cout<<"123 "<<start1->val<<endl;
start2=temp2;
// cout<<"123 "<<start2->val<<endl;
}
}
};
int main()
{
ListNode * x=new ListNode(1);
ListNode * x1=new ListNode(2);
x->next=x1;
//ListNode * x2=new ListNode(3);
// x1->next=x2;
// ListNode * x3=new ListNode(4);
// x2->next=x3;
// ListNode *x4=new ListNode(5);
// x3->next=x4;
Solution s;
s.reorderList(x);
while(x)
{
cout<<x->val<<endl;
x=x->next;
}
return 0;
}