LinkedListSwap.cpp

#include <iostream>
using namespace std;

struct LLnode {
    int data;
    LLnode *next;
};
//Traversal
void display(LLnode *ptr) {
    while(ptr != NULL) {
        cout << "Element: " << ptr->data <<"->";
        ptr = ptr->next;
    }
}
// Function to swap two nodes in a linked list
LLnode *swapNodes(LLnode *head, int value1, int value2) {
    if(value1 == value2) {
        cout<<"Same values,no swaping required."<<endl;
        return head;
    }
    LLnode *prev1 = NULL, *curr1 = head;
    while(curr1 != NULL && curr1->data != value1) {
        prev1 = curr1;
        curr1 = curr1->next;
    }
    LLnode *prev2 = NULL, *curr2 = head;
    while (curr2 != NULL && curr2->data != value2) {
        prev2 = curr2;
        curr2 = curr2->next;
    }

    // If either of the values is not found
    if(curr1 == NULL || curr2 == NULL) {
        cout << "Node not found!" << endl;
        return head;
    }
    // If curr1 is not the head of the list
    if(prev1 != NULL) {
        prev1->next = curr2;
    } else{
        head = curr2;
    }
    // If curr2 is not the head of the list
    if(prev2 != NULL) {
        prev2->next = curr1;
    } else {
        head = curr1;
    }
    // Swap next pointers
    LLnode *temp = curr1->next;
    curr1->next = curr2->next;
    curr2->next = temp;

    return head;
}

int main() {
    LLnode *head, *second, *third, *fourth, *fifth;

    // Allocate memory for nodes in linked list
    head = (struct LLnode *)malloc(sizeof(LLnode));
    second = (struct LLnode *)malloc(sizeof(LLnode));
    third = (struct LLnode *)malloc(sizeof(LLnode));
    fourth = (struct LLnode *)malloc(sizeof(LLnode));
    fifth = (struct LLnode *)malloc(sizeof(LLnode));

    // Initialize data
    head->data = 1;
    head->next = second;
    second->data = 2;
    second->next = third;
    third->data = 3;
    third->next = fourth;
    fourth->data = 4;
    fourth->next = fifth;
    fifth->data = 5;
    fifth->next = NULL;

    cout<<"Before swapping:" << endl;
    display(head);

    head = swapNodes(head, 1, 2);

    cout<<"\nAfter swapping:" << endl;
    display(head);

    return 0;
}