# Untitled

unknown
plain_text
3 years ago
4.1 kB
6
Indexable
Never
```//swap nodes without swapping data
/* This program swaps the nodes of linked list rather
than swapping the field from the nodes.*/

#include <stdio.h>
#include <stdlib.h>

/* A linked list node */
struct Node {
int data;
struct Node* next;
};

/* Function to swap nodes x and y in linked list by
void swapNodes(struct Node** head_ref, int x, int y)
{
// Nothing to do if x and y are same
if (x == y)
return;

// Search for x (keep track of prevX and CurrX
struct Node *prevX = NULL, *currX = *head_ref;
while (currX && currX->data != x) {
prevX = currX;
currX = currX->next;
}

// Search for y (keep track of prevY and CurrY
struct Node *prevY = NULL, *currY = *head_ref;
while (currY && currY->data != y) {
prevY = currY;
currY = currY->next;
}

// If either x or y is not present, nothing to do
if (currX == NULL || currY == NULL)
return;

// If x is not head of linked list
if (prevX != NULL)
prevX->next = currY;
else // Else make y as new head

// If y is not head of linked list
if (prevY != NULL)
prevY->next = currX;
else // Else make x as new head

// Swap next pointers
struct Node* temp = currY->next;
currY->next = currX->next;
currX->next = temp;
}

/* Function to add a node at the beginning of List */
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 */

/* move the head to point to the 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;
}
}

/* Driver program to test above function */
int main()
{
struct Node* start = NULL;

/* The constructed linked list is:
1->2->3->4->5->6->7 */
push(&start, 7);
push(&start, 6);
push(&start, 5);
push(&start, 4);
push(&start, 3);
push(&start, 2);
push(&start, 1);

printf("\n Linked list before calling swapNodes() ");
printList(start);

swapNodes(&start, 4, 3);

printf("\n Linked list after calling swapNodes() ");
printList(start);

return 0;
}

//delete alternate nodes of a linked list
// C program to remove alternate nodes of a linked list
#include<stdio.h>
#include<stdlib.h>

/* A linked list node */
struct Node
{
int data;
struct Node *next;
};

/* deletes alternate nodes of a list starting with head */
void deleteAlt(struct Node *head)
{
if (head == NULL)
return;

/* Initialize prev and node to be deleted */
struct Node *prev = head;
struct Node *node = head->next;

while (prev != NULL && node != NULL)
{
/* Change next link of previous node */
prev->next = node->next;

/* Free memory */
free(node);

/* Update prev and node */
prev = prev->next;
if (prev != NULL)
node = prev->next;
}
}

/* UTILITY FUNCTIONS TO TEST fun1() and fun2() */
/* Given a reference (pointer to pointer) to the head
of a list and an int, push a new node on the front
of the list. */
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 */

/* move the head to point to the 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;
}
}

/* Driver program to test above functions */
int main()
{
/* Start with the empty list */
struct Node* head = NULL;

/* Using push() to construct below list
1->2->3->4->5 */