How to reverse a linked list

Question Posted / imthiaz

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How to reverse a linked list..

Hi,
I have written code for some of the possible questions
asked in Single linked list in C.

Also the code covers the answer for the question asked here.

Here in the code, almost all printf statements may be of two
lines, So if you are directly copiying the code, into ur
compiler u may get errors. So make all the printf to single
line then compile it and see the o/p.

#include<stdio.h>
#include<conio.h>
#define ADDATBEG 1
#define ADDATEND 2
#define INSERT 3
#define DEL 4
#define SEARCH 5
#define SORT 6
#define REVERSE 7
#define NODEFROMEND 8

struct node
{
int data;
struct node *next;
};
struct node *BaseNode = '\0';

/*Function prototypes*/
void AddAtBeg(struct node **BaseNode, int data);
void AddAtEnd(struct node **BaseNode, int data);
void AddAtMid(struct node **BaseNode, int data, int pos);
void DelNode(struct node **BaseNode, int pos);
void DisList(struct node **BaseNode);
void SearchNode(struct node **BaseNode, int data);
void funchoice(int choice);
void SortList(struct node **BaseNode);
void NthNodeFrmEnd(struct node **BaseNode, int n);
void RevList(struct node **BaseNode);

int main()
{
int i, choice;
printf("ENTER THE CHOICE:\n");
printf("1.TO ADD THE NODE AT BEGINING - STACK \n2.TO ADD
THE NODE AT THE END - QUEUE\n");
printf("\nCHOICE:");
scanf("%d", &choice);
funchoice(choice);

printf("\n\nENTER CHOICE \n");
printf("3.TO INSERT NODE\n");
printf("4.TO DEL NODE\n");
printf("5.TO SEARCH GIVEN NODE IN THE LIST\n");
printf("6.TO SORT THE LIST\n");
printf("7.TO REVERSE THE LIST\n");
printf("8.VALUE OF 'N'th FROM LAST\n");
printf("\nCHOICE:");
scanf("%d", &choice);
funchoice(choice);

getch();
}

void funchoice(int choice)
{
int no = 0, element = 0,i;
switch(choice)
{
case ADDATBEG:
printf("\nENTER THE NO OF ELEMENTS TO BE ADDED\n");
scanf("%d", &no);
printf("\nENTER THE ELEMENTS TO BE ADDED IN THE
LIST\n");
for(i = 0; i<no; i++)
{
scanf("%d", &element);
AddAtBeg(&BaseNode, element);

}
DisList(&BaseNode);
break;

case ADDATEND:
printf("\nENTER THE NO OF ELEMENTS TO BE ADDED\n");
scanf("%d", &no);
printf("\nENTER THE ELEMENTS TO BE ADDED IN THE
LIST\n");
for(i = 0; i<no; i++)
{
scanf("%d", &element);
AddAtEnd(&BaseNode, element);
}
DisList(&BaseNode);
break;

case INSERT:
printf("\nENTER THE NODE POSTION WHERE THE NEW NODE
TO BE INSERTED\n");
scanf("%d", &no);
printf("\nENTER THE NO TO BE INSERTED\n");

scanf("%d", &element);
AddAtMid(&BaseNode, element, no);
DisList(&BaseNode);
break;

case DEL:
printf("\nENTER THE NODE POSTION OF THE NODE TO BE
DELETED\n");
scanf("%d", &no);
DelNode(&BaseNode, no);
DisList(&BaseNode);
break;

case SEARCH:
printf("\nENTER THE VALUE TO BE SEARCHED IN THE
LIST\n");
scanf("%d", &element);
SearchNode(&BaseNode, element);
break;

case SORT:
SortList(&BaseNode);
DisList(&BaseNode);
break;

case REVERSE:
RevList(&BaseNode);
DisList(&BaseNode);
break;

case NODEFROMEND:
printf("\nENTER THE NODE POSITION FROM END TO WHICH
THE VALUE HAS TO BE FOUND\n");
scanf("%d", &no);
NthNodeFrmEnd(&BaseNode, no);
break;

default:
exit(0);
break;

}
}
/*To print the data in the linked list*/
void DisList(struct node **BaseNode)
{
struct node *temp;
temp = *BaseNode;
printf("\nNODES IN THE LIST IS \n");
while(temp != '\0')
{
printf("%d ", temp->data);
temp = temp->next;
}
}

/*Stack Implementation*/
void AddAtBeg(struct node **BaseNode, int data)
{
struct node *temp;
temp = (struct node *)malloc(sizeof(struct node));
if(temp != '\0')
{
temp->data = data;
temp->next = *BaseNode;
*BaseNode = temp;
}
}
/*Queue Implementation*/
void AddAtEnd(struct node **BaseNode, int data)
{
struct node *temp, *temp1;
temp = *BaseNode;
if(temp == '\0')
{
/*List is empty - Create first node*/
temp1 = (struct node *)malloc(sizeof(struct node));
if(temp1 != '\0')
{
temp1->data = data;
temp1->next = '\0';
*BaseNode = temp1;
}
}
else
{
/*Node is existing already, So create another node*/
while(temp->next != '\0')
{
temp = temp->next;
}
temp1 = (struct node *)malloc(sizeof(struct node));
if(temp1 != '\0')
{
temp1->data = data;
temp1->next = '\0';
temp->next = temp1;
}
}
}

/*To insert a node between two nodes*/
void AddAtMid(struct node **BaseNode, int data, int pos)
{
/*To insert a node in between to the given node*/
struct node *temp, *temp1;
int count = 0;
temp = *BaseNode;
/*count, the no of nodes available in the list*/
while(temp->next != '\0')
{
count++;
temp = temp->next;
}
/*Check whether the enough nodes are available or not*/
if(pos <= (count+1))
{
temp = *BaseNode;
while(pos-1)
{
temp = temp->next;
pos--;
}
temp1 = (struct node *)malloc(sizeof(struct node));
if(temp1 != '\0')
{
temp1->data = data;
temp1->next = temp->next;
temp->next = temp1;
}
}
else
{
printf("NEW NODE CANT BE ADDED:THERE IS NO ENOUGH
NODES IN THE LIST\n");
}
}

/*To delete a particular node in the list*/
void DelNode(struct node **BaseNode, int pos)
{
struct node *temp, *temp1;
int count = 0, pos1;
temp = *BaseNode;
pos1 = pos;

/*count, the no of nodes available in the list*/
while(temp->next != '\0')
{
count++;
temp = temp->next;
}
/*Check whether the enough nodes are available or not*/
if(pos <= (count+1))
{
temp = *BaseNode;
temp1 = temp->next;
while(pos-2)
{
temp = temp->next;
temp1 = temp1->next;
pos--;
}
temp->next = temp1->next;
printf("\n\nTHE DATA '%d' AT THE NODE '%d' IS
DELETED \n\n", temp1->data, pos1);
free(temp1);
}
else
{
printf("\n\nGIVEN NODE CANT BE DELETED:THERE IS NO
ENOUGH NODES IN THE LIST\n");
}
}

/*To search the given data in the linked list*/
void SearchNode(struct node **BaseNode, int data)
{
struct node *temp;
int count = 0;
temp = *BaseNode;
while(temp != '\0')
{
count++;
if(temp->data == data)
{
printf("\nTHE NODE WITH DATA '%d' FOUND AT
THE POSITION '%d'\n", data, count);
break;
}
else if(temp->next == '\0')
{
printf("\nTHE NODE IS NOT FOUND IN THE
LIST\n");
}
temp = temp->next;
}
}

/*To Sort the linked list in ascending order*/
void SortList(struct node **BaseNode)
{
struct node *temp, *temp1;
int localvar;
temp = *BaseNode;
temp1 = temp->next;
while(temp1 != '\0')
{
if(temp->data > temp1->data)
{
localvar = temp->data;
temp->data = temp1->data;
temp1->data = localvar;
}
temp = temp->next;
temp1 = temp1->next;
}
}

/*To find the 'n'th node from last node of linked list by
traversing the list only once*/
void NthNodeFrmEnd(struct node **BaseNode, int n)
{
struct node *temp, *temp1;
int count = 0;
temp1 = temp = *BaseNode;
while(temp1 != '\0')
{
count++;
temp1 = temp1->next;
}
if(n <= count)
{
count = 0;
temp1 = *BaseNode;
while(temp1->next != '\0')
{
count++;
if(count > n-1)
{
temp = temp->next;
}
temp1 = temp1->next;
}
printf("\nNODE %d FROM LAST, HOLD THE VALUE %d\n",
n, temp->data);
}
else
{
printf("\nTHERE IS NO ENOUGH NODES IN THE LIST\n");

}
}

/*To Reverse a given linked list*/
void RevList(struct node **BaseNode)
{
struct node *Fst, *Sec, *Thrd;
Sec = (*BaseNode)->next;
Thrd = Sec->next;
(*BaseNode)->next = '\0';

while(Thrd != '\0')
{
Sec->next = *BaseNode;
*BaseNode = Sec;
Sec = Thrd;
Thrd = Thrd->next;
}
Sec->next = *BaseNode;
*BaseNode = Sec;
}

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