INTERVIEW QUESTIONS PROGRAMMING LANGUAGES C DETAILS

Question: I want C program code for : Reverse the links of a linked list by traversing only once

Input:
The input consists of the information in each node of the linked list.

Output:
The program displays the information in the linked list after the links are reversed.

Sample Input:
Enter the information in the linked list (Enter -1 to exit): 10
20
30
40
50
-1


Sample Output:
After the links are reversed
Information in the linked list:
50
40
30
20
10

Answer: #include <stdio.h>
#include <malloc.h>
#include <conio.h>


struct Node
{
int a;
Node *next;
};


Node* ReverseList( Node ** List );

void main()
{

struct Node *root,*n,*p;

root=(Node*)malloc(sizeof(Node));
root->a=10;
root->next=NULL;
n=root;
p=(Node*)malloc(sizeof(Node));
p->a=20;
p->next=NULL;
n->next=p;
n=p;
p=(Node*)malloc(sizeof(Node));
p->a=30;
p->next=NULL;
n->next=p;
n=p;
p=(Node*)malloc(sizeof(Node));
p->a=40;
p->next=NULL;
n->next=p;
n=p;
p=(Node*)malloc(sizeof(Node));
p->a=50;
p->next=NULL;
n->next=p;
n=p;
Node *rlist = ReverseList(&root);
int i=1;
while(rlist!=NULL){
printf("element %d =%dn",i++,rlist->a);
rlist=rlist->next;
}
n=root;
while(n!=NULL){
p=n->next;
free(n);
n=p;
}
}


Node* ReverseList( Node ** List )
{

Node *temp1 = *List;

Node * temp2 = NULL;

Node * temp3 = NULL;

while ( temp1 )

{

*List = temp1; //set the head to last node

temp2= temp1->next; // save the next ptr in temp2

temp1->next = temp3; // change next to privous

temp3 = temp1;

temp1 = temp2;

}

return *List;

}

#include <stdio.h>
#include <malloc.h>
#include <conio.h>


struct Node
{
int a;
Node *next;
};


Node* ReverseList( Node ** List );

void main()
{

struct Node *root,*n,*p;

root=(Node*)malloc(sizeof(Node));
root->a=10;
root->next=NULL;
n=root;
p=(Node*)malloc(sizeof(Node));
p->a=20;
p->next=NULL;
n->next=p;
n=p;
p=(Node*)malloc(sizeof(Node));
p->a=30;
p->next=NULL;
n->next=p;
n=p;
p=(Node*)malloc(sizeof(Node));
p->a=40;
p->next=NULL;
n->next=p;
n=p;
p=(Node*)malloc(sizeof(Node));
p->a=50;
p->next=NULL;
n->next=p;
n=p;
Node *rlist = ReverseList(&root);
int i=1;
while(rlist!=NULL){
printf("element %d =%dn",i++,rlist->a);
rlist=rlist->next;
}
n=root;
while(n!=NULL){
p=n->next;
free(n);
n=p;
}
}


Node* ReverseList( Node ** List )
{

Node *temp1 = *List;

Node * temp2 = NULL;

Node * temp3 = NULL;

while ( temp1 )

{

*List = temp1; //set the head to last node

temp2= temp1->next; // save the next ptr in temp2

temp1->next = temp3; // change next to privous

temp3 = temp1;

temp1 = temp2;

}

return *List;

}
Source: CoolInterview.com

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