C++ Linked List Exercises: Reverse linked list

Last update on December 20 2024 12:23:50 (UTC/GMT +8 hours)

Write a C++ program to create a singly linked list of n nodes and display it in reverse order.

Visualization:

Test Data:
Original Linked list:
11 9 7 5 3 1
Reverse Linked list:
1 3 5 7 9 11

Sample Solution:

C++ Code:

#include <iostream> // Including input-output stream header file

using namespace std; // Using standard namespace

//Declare node 
struct node{
    int num; // Data field to store a number
    node *next; // Pointer to the next node
};

//Starting (Head) node
struct node *head=NULL; // Initializing the head node as NULL initially

//Insert node at start
void insert_Node(int n){
    struct node *new_node=new node; // Creating a new node
    new_node->num=n; // Assigning data to the new node
    new_node->next=head; // Pointing the new node to the current head
    head=new_node; // Making the new node as the head
}

// Function to reverse the linked list
void reverse() {
    // Set the current, previous, and next pointers to their initial values
    node* current = head;
    node *prev = NULL, *next = NULL;

    while (current != NULL) {
        // Store next
        next = current->next;
        // Reverse the node pointer for the current node
        current->next = prev;
        // Advance the pointer one position.
        prev = current;
        current = next;
    }
    head = prev; // Make the last node (prev) as the new head of the reversed list
}

//Display all nodes
void display_all_nodes() {
    struct node *temp = head; // Temporary node to traverse the list
    while(temp != NULL) { // Loop to iterate through the list
        cout << temp->num << " "; // Displaying the data in the current node
        temp = temp->next; // Moving to the next node
    }
    cout << endl; // Displaying newline after printing all nodes
}

int main(){
    insert_Node(1); // Inserting a node with value 1
    insert_Node(3); // Inserting a node with value 3
    insert_Node(5); // Inserting a node with value 5
    insert_Node(7); // Inserting a node with value 7
    insert_Node(9); // Inserting a node with value 9
    insert_Node(11); // Inserting a node with value 11

    cout << "Original Linked list:\n";
    display_all_nodes(); // Displaying all nodes in the original list

    cout << "\nReverse Linked list:\n";
    reverse(); // Reversing the linked list
    display_all_nodes(); // Displaying all nodes in the reversed list

    return 0; // Returning from the main function
}

Sample Output:

Original Linked list:
11 9 7 5 3 1 

Reverse Linked list:
1 3 5 7 9 11  

Flowchart:

CPP Code Editor:

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Next C++ Exercise: Count number of nodes in a linked list.