GeeksforGeeks » Linked List specific questions
Given a Singly Linked List, swap elements in pair
(16 posts)-
Given a singly linked list, swap every two elements (e.g. a->b->c->d->e->f->null should become b->a->d->c->f->e->null)
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#include<stdio.h> #include<stdlib.h> struct node { int data; struct node *next; }; /* Function to alternatively swap the elements */ void rearrange(struct node *start) { struct node *p, * q; int temp; if ((!start) || !start->next) return; p = start; q = start->next; while(q) { temp = p->data; p->data = q->data; q->data = temp; p = q->next; q = p?p->next:0; } } /* TESTING rearrange() .............. */ /* Function to push a node */ void push(struct node** head_ref, int new_data) { /* allocate node */ struct node* new_node = (struct node*) malloc(sizeof(struct node)); /* put in the data */ new_node->data = new_data; /* link the old list off the new node */ new_node->next = (*head_ref); /* move the head to point to the new node */ (*head_ref) = new_node; } /* Function to print nodes in a given linked list */ void printList(struct node *node) { while(node != NULL) { printf(" %d ", node->data); node = node->next; } } /* Druver program to test above function */ int main() { struct node *start = NULL; /* The constructed linked list is: 6->5->4->3->2->1 */ push(&start, 1); push(&start, 2); push(&start, 3); push(&start, 4); push(&start, 5); push(&start, 6); printf("\n Original Linked list"); printList(start); rearrange(start); printf("\n Linked list after alternative swaps "); printList(start); getchar(); } -
u hav used three pointers,but dis can be done wid one pointer aloone.
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tempnode=currentnode; currentnoce=currentnode->next; while(currentnode->next!=null) { tempnode->next=currentnode->next; currentnode->next=tempnode; currentnode=tempnode->next->next; tempnode=tempnode->next; } -
Nice. Above only pointers are manipulated. no data is swapped.
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struct node
{
int data;
struct node* next;
};node* first = NULL;
struct node* makenode(int a)
{
node* tmp = new node();
tmp->data = a;
tmp->next = NULL;
return tmp;
}void display()
{
if(first == NULL)
return;node* tmp = first;
do
{
cout << tmp->data << endl;
tmp = tmp->next;
}
while(tmp != NULL);
}void swap()
{
int count = 0;
node* tmp = first;if(tmp == NULL)
return;
do
{
count++;
if(count % 2 == 1)
{
if(tmp->next == NULL)
continue;
int _tmp = tmp->data;
tmp->data = tmp->next->data;
tmp->next->data = _tmp;
}
tmp = tmp->next;
}
while(tmp != NULL);
}int main()
{
first = makenode(1);
first->next = makenode(2);
first->next->next = makenode(3);
first->next->next->next = makenode(4);
first->next->next->next->next = makenode(5);
first->next->next->next->next->next = makenode(6);cout << "Before swapping " << endl;
display();
swap();
cout << "After swapping " << endl;
display();
getch();
} -
void swap(struct node* head){ if(head == NULL ){ return ; } struct node* p = head; struct node* q = head->link; int temp; temp = p->data; p->data = q->data; q->data = temp; swap(q->link); } -
void swap(struct node* head){
if(head == NULL ){
return ;
}
struct node* p = head;
struct node* q = head->link;
int temp;
temp = p->data;
p->data = q->data;
q->data = temp;
swap(q->link);} [center]
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void swap_pair(node *h) { node *temp,*ptr1,*ptr2; temp=null; ptr1=h;ptr2=ptr1->next; while(ptr2) { ptr1->next=ptr2->next; ptr2->next=ptr1; if(temp==null) temp=ptr1; else temp->next=ptr2; ptr1=ptr1->next; ptr2=ptr1->next; } }Plz revert back if i am wrong..
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No error ckecking
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swati baliyan
guest
Posted 7 months ago #
//swap every two elements in an linked list
/* a->b->c->d->e->f->null
b->a->d->c->f->e->null */
#include<stdio.h>
#include<conio.h>
#include<malloc.h>
struct node
{
int data;
struct node *next;
};
struct node *start=NULL;
void create(int);
void swap(int);
void main()
{
int n;
struct node *temp;
printf("enter number of nodes");
scanf("%d",&n);
create(n);
swap(n);
printf("\nafter swapping\n");
if(start!=NULL)
{
temp=start;
while(temp!=NULL)
{
printf("%d ",temp->data);
temp=temp->next;
}
}
}
void create(int n)
{
int i=0;
for(i=0;i<n;i++)
{
struct node *newnode,*temp;
newnode=(struct node *)malloc(sizeof(struct node));
printf("\nenter number\n");
scanf("%d",&newnode->data);
newnode->next=NULL;
if(start==NULL)
start=newnode;
else
{
temp=start;
while(temp->next!=NULL)
{
temp=temp->next;
}
temp->next=newnode;
}
}
}
void swap(int n)
{
int i,c;
struct node *temp,*curr,*mid;
curr=start;
for(i=1;i<=n;i++)
{
if(i%2==1 && curr->next!=NULL)
{
temp=curr;
mid=temp->next;
c=temp->data;
temp->data=mid->data;
mid->data=c;
curr=mid->next;
}
}
} -
just generalizing this to n. (every n element set will be reversed.) ie, 1->2->3->4->5->6, n=3 will be 3->2->1->6->5->4.
node * sortinpartsofn(node *head,int n)
{
int k=n;
if(head==NULL)return NULL;
node *p,*q=NULL,*temp=head;
while(k--)
{
p=q;
q=temp;
temp=temp->next;
q->next=p;
}
head->next=sortinpartsofn(temp,n);
return q;
}NB: This works only if the number of nodes is a multiple of n.
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The name of the function above is a bit misleading. Don't bother. It does not sort.
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#include<stdio.h> #include<stdlib.h> struct LinkedListNode { int data; struct LinkedListNode *next; }; struct LinkedListNode* createNode(int data) { struct LinkedListNode *newNode = (struct LinkedListNode *)malloc(sizeof(struct LinkedListNode)); newNode->data = data; newNode->next = NULL; return newNode; } void printLinkedList(struct LinkedListNode *head) { while(head) { printf("%d ",head->data); head = head->next; } printf("\n"); } void reverseNodeInPairs(struct LinkedListNode *head) { struct LinkedListNode *current = head; int temp; while(current && current->next!=NULL) { temp = current->data; current->data = current->next->data; current->next->data = temp; current = current->next->next; } } int main() { struct LinkedListNode *head = createNode(1); head->next = createNode(2); head->next->next = createNode(3); head->next->next->next = createNode(4); head->next->next->next->next = createNode(5); head->next->next->next->next->next = createNode(6); head->next->next->next->next->next->next = createNode(7); printLinkedList(head); reverseNodeInPairs(head); printLinkedList(head); getchar(); return 1; } -
Another solution for the problem is by interchanging the links of nodes
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#include<stdio.h> #include<stdlib.h> struct LinkedListNode { int data; struct LinkedListNode *next; }; struct LinkedListNode* createNode(int data) { struct LinkedListNode *newNode = (struct LinkedListNode *)malloc(sizeof(struct LinkedListNode)); newNode->data = data; newNode->next = NULL; return newNode; } void printLinkedList(struct LinkedListNode *head) { while(head) { printf("%d ",head->data); head = head->next; } printf("\n"); } void reverseNodeInPairs(struct LinkedListNode **head) { struct LinkedListNode *current = *head; struct LinkedListNode *previous = NULL; struct LinkedListNode *temp; int count=0; while(current && current->next!=NULL) { temp = current->next; if(current==*head) { *head=temp; printf("head : %d\n" ,*head); printf("current : %d\n" ,current); } printf("temp: %d \n",temp->data); current->next = temp->next; printf("current->next: %d \n",current->next->data); temp->next = current; printf("temp ->next: %d \n",current->next->data); if(previous!=NULL) previous->next = temp; previous = current; current = current->next; printf("current: %d \n",current->data); } } int main() { struct LinkedListNode *head = createNode(1); head->next = createNode(2); head->next->next = createNode(3); head->next->next->next = createNode(4); head->next->next->next->next = createNode(5); head->next->next->next->next->next = createNode(6); head->next->next->next->next->next->next = createNode(7); printLinkedList(head); reverseNodeInPairs(&head); printLinkedList(head); getchar(); return 0; }
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