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KReverse.cpp
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KReverse.cpp
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/*
Implement kReverse( int k ) in a linked list i.e. you need to reverse first K elements then reverse next k elements and join the linked list and so on.
Indexing starts from 0. If less than k elements left in the last, you need to reverse them as well. If k is greater than length of LL, reverse the complete LL.
You don't need to print the elements, just return the head of updated LL.
Input format :
Line 1 : Linked list elements (separated by space and terminated by -1)
Line 2 : k
Sample Input 1 :
1 2 3 4 5 6 7 8 9 10 -1
4
Sample Output 1 :
4 3 2 1 8 7 6 5 10 9
Sample Input 2 :
1 2 3 4 5 -1
2
Sample Output 2 :
2 1 4 3 5
Sample Input 3 :
1 2 3 4 5 6 7 -1
3
Sample Output 3 :
3 2 1 6 5 4 7
*/
//Reverse list of size k
#include <bits/stdc++.h>
using namespace std;
//Implement kReverse(int k) i.e. you reverse first k elements then reverse next k elements and so on
class node{
public:
int data;
node * next;
node(int data){
this->data=data;
this->next=NULL;
}
};
void printlist(node *head){
while(head){
cout<<head->data<<" ";
head=head->next;
}
cout<<endl;
}
node* revelist(node *head){
if(head==NULL)
return NULL;
if(head->next==NULL)
return head;
node *prev=head;
node *cur=head->next;
prev->next=NULL;
while(cur){
node *temp=cur->next;
cur->next=prev;
prev=cur;
cur=temp;
}
return prev;
}
int getLenght(node* head){
int c=0;
while(head){
head=head->next;
c++;
}
return c;
}
node* kReverse(node*head,int n)
{
//write your code here
if(head==NULL)
return NULL;
int count=0;
node* front=head;
node* tail=head;
node* newHead;
for(int i=1;i<n;i++){
if(tail->next==NULL)
break;
else
tail=tail->next;
}
node *newtail=front;
node *temp=tail->next;
tail->next=NULL;
newHead=revelist(front);
node* ans=kReverse(temp,n);
newtail->next=ans;
return newHead;
}
node* takeinput(){
int data;
cin>>data;
node* head=NULL,*tail=NULL;
while(data!=-1){
node *newnode=new node(data);
if(head==NULL) {
head=newnode;
tail=newnode;
}
else{
tail->next=newnode;
tail=newnode;
}
cin>>data;
}
return head;
}
void print(node *head)
{
node*temp=head;
while(temp!=NULL)
{
cout<<temp->data<<" ";
temp=temp->next;
}
cout<<endl;
}
int main()
{
node* head=takeinput();
int n;
cin>>n;
head=kReverse(head,n);
print(head);
return 0;
}