Question:

How to Expand a linked list of numbers by one using C++?

Summary:

Here our task is to add one to each digit available in the array and create a new array.

Solution:

//User function template for C++

struct Node

{

int data;

struct Node* next;

Node(int x){

data = x;

next = NULL;

}

};

class Solution

{

private:

Node* reverse(Node* head){

Node* curr = head;

Node* prev = NULL;

while(curr!=NULL){

Node* forward = curr->next;

curr->next = prev;

prev = curr;

curr = forward;

}

return prev;

}

void InsertAtTail(Node* &head,Node* &tail,int value){

Node* temp = new Node(value);

if(head==NULL){

head = temp;

tail = temp;

}

else{

tail->next = temp;

tail = temp;

}

public:

Node* addOne(Node *head)

{

// Your Code here

// return head of list after adding one

Node* temp = reverse(head);

Node* ansh = NULL;

Node* anst = NULL;

int carry = 1;

int sum=0;

while(temp!=NULL||carry!=0){

if(temp!=NULL){

sum = temp->data + carry;

temp = temp->next;

}

else{

sum = carry;

}

int digit = sum%10;

InsertAtTail(ansh,anst,digit);

carry = sum/10;

}

return reverse(ansh);

}

};

// class Solution {

// private:

// Node* reverse(Node* head) {

// Node* curr = head;

// Node* prev = NULL;

// while(curr != NULL){

// Node* forward = curr->next;

// curr->next = prev;

// prev = curr;

// curr = forward;

// }

// return prev; // Return the new head of the reversed list

// }

// void InsertAtTail(Node* &head, Node* &tail, int value) {

// Node* temp = new Node(value);

// if(head == NULL){

// head = temp;

// tail = temp;

// }

// else{

// tail->next = temp;

// tail = temp;

// }

// public:

// Node* addOne(Node *head) {

// head = reverse(head);

// Node* temp = head;

// Node* ansh = NULL;

// Node* anst = NULL;

// int carry = 1;

// while(temp != NULL || carry != 0) {

// int sum = (temp != NULL ? temp->data : 0) + carry;

// int digit = sum % 10;

// InsertAtTail(ansh, anst, digit); // Insert the digit, not the carry

// carry = sum / 10;

// if (temp != NULL) {

// temp = temp->next;

// }

// return reverse(ansh); // Reverse the result back to the original order

// }

// };

Explanation:

Node Structure: Defines a structure for linked list nodes with data and a next pointer. It includes a constructor to initialize data and the next pointer.

Private Function reverse: Reverses a given linked list and returns the head of the reversed list. It iterates through the list, reversing the pointers.

Private Function InsertAtTail: Inserts a new node with the given value at the tail of a linked list. If the list is empty, it initializes both the head and tail pointers.

Public Function addOne: Adds one to a given linked list, which represents a non-negative integer. It first reverses the list using the reverse function. Then, it iterates through the reversed list, adding one to each digit and updating the carry. Finally, it reverses the resulting list again and returns the head.

The commented-out code below the main code snippet provides an alternative implementation for the addOne function with the same logic but different variable naming and commenting style.

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