I am new for c programming ,i have tried myself inserting node in singly linked list program but i didn't get a proper output and i dont have any idea to correct my program if anybody knows please help.
#include<stdio.h>
#include<stdlib.h>
struct node
{
int data;
struct node *next;
}*head;
int loc;
void addbegin(int num)
{
struct node *temp;
temp=(struct node *)malloc(sizeof(struct node));
temp->data=num;
if(head=NULL)
{
head=temp;
head->next=NULL;
}
else
{
temp->next=head;
head=temp;
}
}
void addend(int num)
{
struct node *temp1,*temp2;
temp1=(struct node *)malloc(sizeof(struct node));
temp1->data=num;
temp2=head;
if(head==NULL)
{
head=temp1;
head->next=NULL;
}
else
{
while(temp2->next != NULL)
temp2=temp2->next;
temp1->next=NULL;
temp2->next=temp1;
}
}
void pos(int num,int loc)
{
int length();
struct node *temp,*cur_ptr,*prev_ptr;
int i;
cur_ptr=head;
if(loc > (length()+1) || loc<= 0)
{
printf("it is illegal call:");
}
else
{
if(loc == 1)
{
addbegin(num);
}
else
{
for(i=1;i<loc;i++)
{
prev_ptr=cur_ptr;
cur_ptr=cur_ptr->next;
}
temp=(struct node*)malloc(sizeof(struct node));
temp->data=num;
prev_ptr->next=temp;
temp->next=cur_ptr;
}
}
}
int length()
{
struct node *cur_ptr;
int count = 0;
cur_ptr=head;
while(cur_ptr!=NULL)
{
cur_ptr=cur_ptr->next;
count++;
}
return(count);
}
void display()
{
struct node *temp=NULL;
if(temp==NULL)
{
printf("list is empty:");
}
while(temp!=NULL)
{
printf("%d",temp->data);
temp=temp->next;
}
}
int main()
{
int num;
head=NULL;
int choice;
while(1)
{
printf("\nList Operations\n");
printf("===============\n");
printf("1.Insert at begin\n");
printf("2.insert at end\n");
printf("3.insert at selected position\n");
printf("4.Display\n");
printf("5.Exit\n");
printf("Enter your choice : ");
if(scanf("%d",&choice)<=0)
{
printf("Enter only an Integer\n");
}
printf("enter your choice:");
scanf("%d",&choice);
switch(choice)
{
case 1: printf("Enter the number to insert at begin : ");
scanf("%d",&num);
addbegin(num);
break;
case 2: printf("Enter the number to insert at end: ");
scanf("%d",&num);
addend(num);
break;
case 3: printf("Enter the number to insert at selected position: ");
scanf("%d",&num);
pos(num,loc);
break;
case 4: printf("display the values");
display();
break;
case 5: printf("exit");
display();
}
}
return 0;
}
i think the error is in my main function but am not clear in that please help
In your addbeginmethod there's at least one obvious error:
if(head=NULL)
should be
if (head == NULL)
as you need to compare, not assign.
In your posmethod you have a function declaration: int length(); which shouldn't be there, but rather at the top, before main.
Another issue, this time in the display method:
void display()
{
struct node *temp=NULL;
if(temp==NULL) {
printf("List is empty:");
}
while(temp!=NULL) {
printf("%d",temp->data);
temp=temp->next;
}
}
Here temp will always be NULL, I guess you meant to assign headto the temppointer, otherwise it will never traverse the list.
And finally, in the insert at specific position choice you need to ask for a location value and pass that along too the function call, so add a declaration for int loc;in main, and change the third case to this:
case 3:
printf("Enter the number to insert at selected position: ");
scanf("%d",&num);
printf("Enter the position: ");
scanf("%d",&loc);
pos(num,loc);
break;
to the
Finally I'm going to quote from the C99 standard, section 5.1.2.2.1 Program startup:
The function called at program startup is named main. The implementation declares no prototype for this function. It shall be defined with a return type of int and with no parameters:
int main(void) { /* ... */ }
or with two parameters (referred to here as argc and argv, though any names may be used, as they are local to the function in which they are declared):
int main(int argc, char *argv[]) { /* ... */ }
So, please, change your declaration of mainand include a returnline at the end (possibly return 0;indicating successful program exit).
This became rather lengthy. After the suggested changes your program should look something like this:
#include<stdio.h>
#include<stdlib.h>
struct node {
int data;
struct node *next;
}*head;
void addbegin(int num)
{
struct node *temp;
temp = malloc(sizeof(struct node));
temp->data=num;
if(head==NULL) {
head=temp;
head->next=NULL;
} else {
temp->next=head;
head=temp;
}
}
void addend(int num)
{
struct node *temp1, *temp2;
temp1 = malloc(sizeof(struct node));
temp1->data = num;
temp2 = head;
if(head == NULL) {
head = temp1;
head->next = NULL;
} else {
while(temp2->next != NULL)
temp2=temp2->next;
temp1->next=NULL;
temp2->next=temp1;
}
}
int length()
{
struct node *cur_ptr;
int count = 0;
cur_ptr = head;
while(cur_ptr != NULL) {
cur_ptr = cur_ptr->next;
count++;
}
return (count);
}
void pos(int num, int loc)
{
struct node *temp, *cur_ptr, *prev_ptr;
int i;
cur_ptr=head;
if(loc > (length()+1) || loc<= 0) {
printf("it is illegal call:");
} else {
if(loc == 1) {
addbegin(num);
} else {
for(i=1; i<loc; i++) {
prev_ptr=cur_ptr;
cur_ptr=cur_ptr->next;
}
temp = malloc(sizeof(struct node));
temp->data=num;
prev_ptr->next=temp;
temp->next=cur_ptr;
}
}
}
void display()
{
struct node *temp = head;
if(temp == NULL) {
printf("List is empty:");
}
printf("The list contains the following values:\n");
while(temp!=NULL) {
printf("%d\n",temp->data);
temp=temp->next;
}
}
int main()
{
int choice, num, loc;
head = NULL;
while(1) {
printf("\nList Operations\n");
printf("===============\n");
printf("1.Insert at begin\n");
printf("2.insert at end\n");
printf("3.Insert at selected position\n");
printf("4.Display\n");
printf("5.Exit\n");
printf("Enter your choice : ");
if(scanf("%d",&choice)<=0) {
printf("Enter only an Integer\n");
}
switch(choice) {
case 1:
printf("Enter the number to insert at begin : ");
scanf("%d",&num);
addbegin(num);
break;
case 2:
printf("Enter the number to insert at end: ");
scanf("%d",&num);
addend(num);
break;
case 3:
printf("Enter the number to insert at selected position: ");
scanf("%d",&num);
printf("Enter the position: ");
scanf("%d",&loc);
pos(num,loc);
break;
case 4:
printf("Display the values\n");
display();
break;
case 5:
printf("exit");
exit(0); // maybe you should exit here.
display();
}
}
return 0;
}