this program creates a sorted list and then inserts an element such that the list still remains sorted. I think the logic is ok..but the program doesn't print the new list formed.Here is the code. what is wrong?
#include<stdio.h>
#include<malloc.h>
#include<stdlib.h>
struct list {
int number;
struct list *next;
};
typedef struct list node;
void create(node *);
void print(node *);
void sortedInsert(node **);
main() {
int user_response;
node *head;
head = (node *)malloc(sizeof(node));
create(head);
printf("Look at your creation!! A linked list!!1 heheheh...........\n");
print(head);
printf("Do you want to experience some \"sort\" of thrill?\n1 for yes..\n");
scanf("%d",&user_response);
if(user_response == 1) {
sortedInsert(&head);
printf("Look at the marvel of linked list...\n");
print(head);
}
else {
printf("Ha\n tired fellow,lack of ambition!!!\n");
exit(0);
}
return 0;
}
void create(node *head) {
printf("Enter a number,-999 to stop\n");
scanf("%d",&head->number);
if(head->number == -999) {
head->next = NULL;
}
else {
head->next = (node *)malloc(sizeof(node));
create(head->next);
}
}
void print(node *head) {
if(head->next != NULL) {
printf("%d-->",head->number);
print(head->next);
}
else {
printf("%d",head->number);
}
}
void sortedInsert(node **headRef) {
node *new_node;
node *prev_ptr = *headRef;
node *dummy_ptr = *headRef;
int key;
printf("Which value do you wanna insert\n");
scanf("%d",&key);
new_node = (node *)malloc(sizeof(node));
new_node->number = key;
while((*headRef)->next != NULL) {
if((*headRef)->number >= key) {
prev_ptr->next = new_node;
new_node->next = *headRef;
*headRef = dummy_ptr;
}
else {
prev_ptr = *headRef;
*headRef = (*headRef)->next;
}
}
Related
I want my code to display the original input 3 -> 2-> 1-> and not display the reversed one.
The output is displaying the 1-> 2-> 3-> . I want to see the original input without ruining the codes. How can I do that? Our professor taught us the concept of linked list and it is connected in this program to input a number and check if it is a palendrome
#include <stdio.h>
#include <stdlib.h>
struct node {
int data;
struct node* next;
};
void insertNum(struct node** head, int number) {
struct node* temp = malloc(sizeof(struct node));
temp -> data = number;
temp -> next = *head;
*head = temp;
}
void display(struct node* head) {
struct node* printNode = head;
printf("displaying list1...\n");
printf("displaying the converted list..\n");
while (printNode != NULL) {
if (printNode->next)
printf("%d->",printNode->data);
else
printf("%d->NULL\n",printNode->data);
printNode=printNode->next;
}
}
struct node* reverseLL(struct node* head) {
struct node* reverseNode = NULL, *temp;
if (head == NULL) {
printf("\nThe list is empty.\n\n");
exit(0);
}
while (head != NULL) {
temp = (struct node*) malloc(sizeof(struct node));
temp -> data = head -> data;
temp -> next = reverseNode;
reverseNode = temp;
head = head -> next;
}
return reverseNode;
}
int check(struct node* LLOne, struct node* LLTwo) {
while (LLOne != NULL && LLTwo != NULL) {
if (LLOne->data != LLTwo->data)
return 0;
LLOne = LLOne->next;
LLTwo = LLTwo->next;
}
return (LLOne == NULL && LLTwo == NULL);
}
void deleteList(struct node** display) {
struct node* temp = *display;
while (temp != NULL) {
temp = temp->next;
free(*display);
*display = temp;
}
}
int main() {
int inputNum, countRun = 0, loop;
char choice;
struct node* reverseList;
struct node* head = NULL;
do {
printf("%Run number : %d\n", ++countRun);
printf("Enter 0 to stop building the list, else enter any integer\n");
printf("Enter list to check whether it is a palindrome... \n");
do {
scanf("%d", &inputNum);
if (inputNum == 0)
break;
insertNum(&head, inputNum);
} while (inputNum != 0);
display(head);
reverseList = reverseLL(head);
if ((check(head, reverseList)) == 1)
printf("\nPalindrome list.\n\n");
else
printf("\nNot palindrome.\n\n");
deleteList(&head);
} while (countRun != 2);
system("pause");
return 0;
}
Your insertNum inserts at the front of the list.
You need a version that appends at the back of the list:
void
appendNum(struct node **head, int number)
{
struct node *temp = malloc(sizeof(struct node));
struct node *cur;
struct node *prev;
temp->data = number;
// find tail of the list
prev = NULL;
for (cur = *head; cur != NULL; cur = cur->next)
prev = cur;
// append after the tail
if (prev != NULL)
prev->next = temp;
// insert at front (first time only)
else
*head = temp;
}
Here is the full code:
#include <stdio.h>
#include <stdlib.h>
struct node {
int data;
struct node *next;
};
void
appendNum(struct node **head, int number)
{
struct node *temp = malloc(sizeof(struct node));
struct node *cur;
struct node *prev;
temp->data = number;
// find tail of the list
prev = NULL;
for (cur = *head; cur != NULL; cur = cur->next)
prev = cur;
// append after the tail
if (prev != NULL)
prev->next = temp;
// insert at front (first time only)
else
*head = temp;
}
void
insertNum(struct node **head, int number)
{
struct node *temp = malloc(sizeof(struct node));
temp->data = number;
temp->next = *head;
*head = temp;
}
void
display(struct node *head)
{
struct node *printNode = head;
printf("displaying list1...\n");
printf("displaying the converted list..\n");
while (printNode != NULL) {
if (printNode->next)
printf("%d->", printNode->data);
else
printf("%d->NULL\n", printNode->data);
printNode = printNode->next;
}
}
struct node *
reverseLL(struct node *head)
{
struct node *reverseNode = NULL,
*temp;
if (head == NULL) {
printf("\nThe list is empty.\n\n");
exit(0);
}
while (head != NULL) {
temp = (struct node *) malloc(sizeof(struct node));
temp->data = head->data;
temp->next = reverseNode;
reverseNode = temp;
head = head->next;
}
return reverseNode;
}
int
check(struct node *LLOne, struct node *LLTwo)
{
while (LLOne != NULL && LLTwo != NULL) {
if (LLOne->data != LLTwo->data)
return 0;
LLOne = LLOne->next;
LLTwo = LLTwo->next;
}
return (LLOne == NULL && LLTwo == NULL);
}
void
deleteList(struct node **display)
{
struct node *temp = *display;
while (temp != NULL) {
temp = temp->next;
free(*display);
*display = temp;
}
}
int
main()
{
int inputNum, countRun = 0, loop;
char choice;
struct node *reverseList;
struct node *head = NULL;
do {
printf("%Run number : %d\n", ++countRun);
printf("Enter 0 to stop building the list, else enter any integer\n");
printf("Enter list to check whether it is a palindrome... \n");
do {
scanf("%d", &inputNum);
if (inputNum == 0)
break;
#if 0
insertNum(&head, inputNum);
#else
appendNum(&head, inputNum);
#endif
} while (inputNum != 0);
display(head);
reverseList = reverseLL(head);
if ((check(head, reverseList)) == 1)
printf("\nPalindrome list.\n\n");
else
printf("\nNot palindrome.\n\n");
deleteList(&head);
} while (countRun != 2);
system("pause");
return 0;
}
I have a circular doubly linked list.
The deletefront() function is not working: the output is wrong. What is the mistake?
The other functions are working. But I get a wrong output after displaying after calling deletefront function. The 100 value which should be deleted is still appearing. Please correct it.
I have included the C source code:
// circular doubly linked list
#include <stdio.h>
#include <stdlib.h>
typedef struct node {
int data;
struct node *rlink;
struct node *llink;
} node;
node *head = NULL;
node *getnode(int ele) {
node *ptr;
ptr = (node *)malloc(sizeof(node));
if (ptr == NULL) {
printf("memory not alloc");
exit(0);
}
if (ptr != NULL) {
ptr->data = ele;
ptr->rlink = NULL;
ptr->llink = NULL;
}
return ptr;
}
void insertfront(int ele) {
node *newnode;
newnode = getnode(ele);
if (head == NULL) {
head = newnode;
head->rlink = head;
head->llink = head;
} else {
head->llink = newnode;
newnode->rlink = head;
head = newnode;
}
}
void insertend(int ele) {
node *newnode;
newnode = getnode(ele);
if (head == NULL) {
head = newnode;
head->rlink = head;
head->llink = head;
} else {
node *temp = head;
do {
temp = temp->rlink;
} while (temp != head->llink);
newnode->rlink = temp->rlink;
temp->rlink = newnode;
newnode->llink = temp;
}
}
int lenlist() {
node *temp;
int count = 0;
temp = head;
do {
temp = temp->rlink;
count++;
} while (temp != head);
return count;
}
void insertatpos(int ele,int pos) {
if (pos == 1) {
insertfront(ele);
} else
if (pos == (lenlist() + 1)) {
insertend(ele);
} else
if (pos > 1 && pos <= (lenlist() + 1)) {
node *prev, *curr;
node *newnode = getnode(ele);
int count = 1;
curr = head;//curr points to 1st node
do {
prev = curr;
count++;
curr = curr->rlink;
if (count == pos) {
prev->rlink = newnode;
newnode->llink = prev;
newnode->rlink = curr;
curr->llink = newnode;
}
} while (curr != head);
} else {
printf("invalid position");
}
}
void delfront() {
if (head == NULL)
printf("empty list");
node *aux;
node *lastnode, *secondnode;
aux = head;
lastnode = head->llink;
secondnode = head->rlink;
secondnode->llink = lastnode;
lastnode->rlink = secondnode;
free(aux);
head = secondnode;
}
void display() {
node *aux = head;
do {
printf("%d->", aux->data);
aux = aux->rlink;
} while (aux != head);
printf("\n");
}
int main() {
insertfront(100);
insertend(20);
printf("\n%d\n", lenlist());
insertatpos(45, 2);
display();
delfront();
display();
}
The problem is not in the deletefront() function, instead, you have missed updating a few links in the insertfront() and insertend() functions.
I have updated the code here and also added the comment where I made the changes. Try to visualise it using an example.
However, I suggest that you solve such issues using a debugger or go through the code with a sample test case. It will improve you debugging as well as coding skills!
Your code have a lot of mistakes.
// circular doubly linked list
#include <stdio.h>
#include <stdlib.h>
/*i changed the names of your pointers here*/
typedef struct node {
int data;
struct node *prev, *next;
} node;
/*
node *head = NULL;
This will be removed.
Avoid using globals as much as you can.
*/
/*
This function is unecessary.
node *createNode(int ele) {
node *ptr;
ptr = (node *)malloc(sizeof(node));
if (ptr == NULL) {
printf("memory not alloc");
exit(0);
}
if (ptr != NULL) {
ptr->data = ele;
ptr->rlink = NULL;
ptr->llink = NULL;
}
return ptr;
}
*/
char insertFront(node **head, int ele) {
node *newNode=malloc(sizeof(node));
If (newNode==NULL) return 0;
newNode->data=ele;
if (*head){
newNode->next=*head;
newNode->prev=(*head)->prev;
(*head)->prev->next=newNode;
(*head)->prev=newNode;
} else {
newNode->next=newNode;
newNode->prev=newNode;
}
*head=newNode;
return 1;
}
char insertEnd(node **head, int ele) {
node *newNode=malloc(sizeof(node));
If (newNode==NULL) return 0;
newNode->data=ele;
if (*head){
newNode->next=*head;
newNode->prev=(*head)->prev;
(*head)->prev->next=newNode;
(*head)->prev=newNode;
} else {
newNode->next=newNode;
newNode->prev=newNode;
*head=newNode;
}
return 1;
}
/*You could simple create a struct list that would have as members
the head of your list and its height to avoid calculating it each time
you want it but anyway. I will fix that.
int lenList(node *head) {
if (*head==NULL) return 0;
node *temp=head;
int count = 0;
do {
temp = temp->next;
count++;
} while (temp != head);
return count;
}
*/
char insertNatP(node **head, int ele, int pos) {
If (pos<1 || pos>lenList(head)){
printf("Invalid Position\n");
return 0;
}
int i;
for(i=0; i<pos-1; head=&head->next, i++);
node *newNode=malloc(sizeof(node));
If (newNode==NULL){
printf("Memory could not be allocated\n");
return 0;
}
newNode->data=ele;
If (*head!=NULL){
newNode->prev=(*head)->prev;
(*head)->prev->next=newNode;
(*head)->prev=newNode
newNode->next=*head;
} else {
newNode->prev=newNode;
newNode->next=newNode;
}
*head=newNode;
return 1;
}
char delFront(node **head) {
if (*head == NULL) return 0;
node garbage=*head;
*head=(*head)->next;
if (*head==garbage) *head=NULL; else{
(*head)->prev=garbage->prev;
garbage->prev->next=*head;
}
free(garbage);
return 1;
}
void printList(node *list) {
if (list==NULL) return;
node *sentinel=list->prev;
while (list!=sentinel) {
printf("%d->", list->data);
list=list->next;
}
printf("%d\n", list->data);
}
int main() {
node *l1=NULL;
insertFront(&l1, 100);
insertEnd(&l1, 20);
printf("\n%d\n", lenList(l1));
insertNatP(&l1, 45, 2);
printList(l1);
delFront(&l1);
printList(l1);
}
Try this
Please point out the error in the code.
The function insertatend() inserts for the first time but not again.
I'm trying to insert a node at the end of a circular linked list, but after inserting an element for the first time, it gets stuck in the while loop if we try to enter data again.
struct node {
int data;
struct node *next;
};
typedef struct node node;
node *head = NULL;
node *insertatend(node *head, int value)
{
node *temp, *p;
p = head;
temp = (node *)malloc(sizeof(node));
temp->data = value;
temp->next = head;
if (head == NULL)
{
head = temp;
}
else
{
while (p->next != head)
p = p->next;
p->next = temp;
}
return head;
}
void display(node *head)
{
node *p = head;
if (head == NULL)
{
printf("\nlinked list is empty\n");
return;
}
while (p->next != head)
{
printf("%d ", p->data);
p = p->next;
}
printf("\n");
}
int main()
{
int ch = 1, value;
while (ch)
{
printf("1.Insert 2.Display");
scanf("%d", &ch);
switch (ch)
{
case 1:
printf("enter an element:");
scanf("%d", &value);
head = insertatend(head, value);
break;
case 2:
display(head);
break;
}
}
return 0;
}
I think the mistake is here:
temp->next=head;
if(head==NULL){
head=temp;
}
When you enter your first element, head is null. So temp->next is set to NULL and head is set to temp.
When you enter your second element, it does this:
else{
while(p->next!=head)
p=p->next;
p->next=temp;}
Where p->next is null, so you will never have the situation that p->next == head and you will always be in the loop!
Edit:
So the solution aproach would be to change it to:
if(head==NULL){
head=temp;
}
temp->next=head;
Edit: second mistake in the display function: the loop doesn't print the last element. I just tested it and it is working fine.
So the complete code woud look like:
#include <stdio.h>
#include <stdlib.h>
struct node {
int data;
struct node *next;
};
typedef struct node node;
node *head = NULL;
node *insertatend(node *head, int value)
{
node *temp, *p;
p = head;
temp = (node *)malloc(sizeof(node));
temp->data = value;
if (head == NULL)
{
head = temp;
}
else
{
while (p->next != head)
p = p->next;
p->next = temp;
}
temp->next = head;
return head;
}
void display(node *head)
{
node *p = head;
if (head == NULL)
{
printf("\nlinked list is empty\n");
return;
}
do
{
printf("%d ", p->data);
p = p->next;
} while (p != head);
printf("\n");
}
int main()
{
int ch = 1, value;
while (ch)
{
printf("1.Insert 2.Display");
scanf("%d", &ch);
switch (ch)
{
case 1:
printf("enter an element:");
scanf("%d", &value);
head = insertatend(head, value);
break;
case 2:
display(head);
break;
}
}
return 0;
}
Alternate version, using tail pointer instead of head pointer, for faster appends.
#include <stdlib.h>
#include <stdio.h>
struct node {
struct node *next;
int data;
};
typedef struct node node;
node *insertatend(node *tail, int value)
{
node *p;
p = malloc(sizeof(node));
p->data = value;
if(tail == NULL){
p->next = p;
} else {
p->next = tail->next;
tail->next = p;
}
return p;
}
void display(node *tail)
{
node *p = tail;
if (p == NULL)
{
printf("\nlinked list is empty\n");
return;
}
do{
p = p->next;
printf("%d ", p->data);
}while(p != tail);
printf("\n");
}
int main()
{
node *tail = NULL;
int i;
for(i = 0; i < 8; i++)
tail = insertatend(tail, i);
display(tail);
return 0;
}
I put together a few pieces of code to make a linked list that adds to head(Has a special function) and in the middle(also special function).
my problem is, i need to provide the program with numbers and insert them as nodes in my LINKEDLIST. However, my display function(to display the tree of nodes) gives back segmentation fault and so does just taking values in without any display function.
I'm fairly new to malloc so i suspect the problem is there?
Thanks
#include<stdio.h>
#include<stdlib.h>
/*LINKEDLIST STRUCT*/
struct node {
int data;
struct node *next;
};
/*Inserting head-Node*/
struct node *insert_head(struct node *head, int number)
{
struct node *temp;
temp = malloc(sizeof(struct node));
if(temp == NULL)
{
printf("Not enough memory\n");
exit(1);
}
temp->data = number;
temp->next = head;
head = temp;
return head;
}
/*Inserting inside a list*/
void after_me(struct node *me, int number)
{
struct node *temp;
temp = malloc(sizeof(struct node));
if(temp == NULL)
{
printf("Not enough memory\n");
exit(1);
}
temp->data = number;
temp->next = me->next;
me->next = temp;
}
/*PRINTING LIST*/
void display(struct node *head)
{
struct node *moving_ptr = head;
while(moving_ptr != NULL)
{
printf("%d-->",moving_ptr->data);
moving_ptr = moving_ptr->next;
}
}
int main()
{
int index;
struct node *head;
struct node *previous_node;
scanf("%d", &index);
while(index > 0)
{
/*allocating in List */
if(head == NULL)
head = insert_head(head,index);
else
if((head != NULL) && (index <= (head->data)))
{
struct node *temp;
head->next = temp;
temp->next = head;/*TRY INSERT HEAD FUNC.*/
}
else
if((head != NULL) && (index > (head->data)))
{
previous_node->data = index-1;
after_me(previous_node,index);
}
scanf("%d", &index);
}
display(head);
}
I suggest as follows.
#include <stdio.h>
#include <stdlib.h>
struct node {
int data;
struct node *next;
};
//aggregated into one place
struct node *new_node(int number){
struct node *temp;
if(NULL == (temp = malloc(sizeof(*temp)))){
printf("\nNot enough memory\n");
exit(1);
}
temp->data = number;
temp->next = NULL;
return temp;
}
struct node *insert_head(struct node *head, int number) {
struct node *temp = new_node(number);
temp->next = head;
return temp;
}
void after_me(struct node *me, int number){
struct node *temp = new_node(number);
temp->next = me->next;
me->next = temp;
}
void display(struct node *head){
struct node *moving_ptr = head;
while(moving_ptr != NULL){
printf("%d", moving_ptr->data);
if(moving_ptr = moving_ptr->next)
printf("-->");
}
putchar('\n');
}
struct node *insert(struct node *me, int number){
if(me){
if(number <= me->data){
me = insert_head(me, number);
} else {
me->next = insert(me->next, number);
}
} else {
me = new_node(number);
}
return me;
}
void release(struct node *list){//Of course, you will be able to replace a simple loop(e.g while-loop).
if(list){
release(list->next);
free(list);
}
}
int main(void){
struct node *head = NULL;
int index;
while(1==scanf("%d", &index) && index > 0){
head = insert(head, index);
}
display(head);
release(head);
return 0;
}
I am writing a linked list program
to add items and display those items.
I am able to add first item successfully,
but error occurs while adding the second item.
I tried to figure out the error,but
everything looks fine to me.
The program hangs,here is my code:
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
struct link_list
{
int number;
struct link_list *next;
};
typedef struct link_list node;
node *head;
void add(int num)
{
node *newnode,*current;
newnode = (node *)malloc(sizeof(node));
newnode->number = num;
newnode->next = NULL;
if(head == NULL)
{
head = newnode;
current = newnode;
}
else
{
current->next = newnode;
current = newnode;
}
}
void display(node *list)
{
list = head;
if(list == NULL)
{
return;
}
while(list != NULL)
{
printf("%d",list->number);
list = list -> next;
}
printf("\n");
}
int main()
{
int i,num;
node *n;
head=NULL;
while(1)
{
printf("\nList Operations\n");
printf("===============\n");
printf("1.Insert\n");
printf("2.Display\n");
printf("3.Exit\n");
printf("Enter your choice : ");
if(scanf("%d",&i)<=0)
{
printf("Enter only an Integer\n");
exit(0);
}
else
{
switch(i)
{
case 1:
printf("Enter the number to insert : ");
scanf("%d",&num);
add(num);
break;
case 2:
if(head==NULL)
{
printf("List is Empty\n");
}
else
{
printf("Element(s) in the list are : ");
}
display(n);
break;
case 3: return 0;
default: printf("Invalid option\n");
}
}
}
return 0;
}
The issue is with the value of current not persisting across function calls. Either move it outside of the function (i.e. right below the head declaration), or declare it as static.
just one change , define your current pointer outside the scope of void add
node *head,*current;
here is the correct code
struct link_list
{
int number;
struct link_list *next;
};
typedef struct link_list node;
node *head,*current;
void add(int num)
{
node *newnode;
newnode = (node *)malloc(sizeof(node));
newnode->number = num;
newnode->next = NULL;
if(head == NULL)
{
head = newnode;
current = newnode;
}
else
{
current->next = newnode;
current = newnode;
}
}