Question

Create a linked list with the following features.

A Node class that stores the data type of your choice.

A constructor that creates a dummy header node.

void display() -- A method for printing the list.

void add(item) -- A method for adding a value to the beginning of the list

void addEnd(item) -- A method of adding a value to the end of the list.

bool contains(item) -- A method for finding a specified value in the list.

int count() -- A method for returning the number of values in the list.

int count(item) -- A method for counting the number of instances of a specified value in the list.

int remove(item) -- A method for deleting a value from the list.

A destructor for destroying the list.

Write a test program in C++ that creates a linked list and demonstrates all of the above functions.

Answer 1

#include<iostream>

using namespace std;

struct Node
{
    int data;
    Node *next;
};

class LinkedList
{
private:
    Node *head;
public:
    //Constructor
    LinkedList();

    //Prints the list
    void display() const;

    //Insert in front of list
    void add(int item);

    //Insert in front of list
    void addEnd(int item);

    //Check if item is in list or not
    bool contains(int item);

    //Return number of values in the list
    int count();

    //Return number of values of specified item in the list
    int count(int item);

    //Remove item from list
    void remove(int item);

    //Destructor
    ~LinkedList();
};

//Constructor
LinkedList::LinkedList() : head(nullptr) {}

//Prints the list
void LinkedList::display() const{
    Node *ptr = head;
    while(ptr != nullptr)
    {
        cout << ptr->data << " ";
        ptr = ptr->next;
    }
}

//Insert in front of list
void LinkedList::add(int item){
    Node *newNode = new Node;
    newNode->data = item;
    newNode->next = nullptr;
    if(head == nullptr)//When list is empty
        head = newNode;
    else
    {
        newNode->next = head;
        head = newNode;
    }
}

//Insert in front of list
void LinkedList::addEnd(int item){
    Node *newNode = new Node;
    newNode->data = item;
    newNode->next = nullptr;

    if(head == nullptr)
        head = newNode;
    else {
        Node *ptr = head;
        while (ptr->next != nullptr)
            ptr = ptr->next;
        ptr->next = newNode;
    }
}

//Check if item is in list or not
bool LinkedList::contains(int item){
    Node *ptr = head;
    while(ptr != nullptr && ptr->data != item)
        ptr = ptr->next;

    if(ptr == nullptr)//If value not found in the list
        return false;

    return true;
}

//Return number of values in the list
int LinkedList::count(){
    Node *ptr = head;
    int count = 0;

    while(ptr != nullptr) {
        count++;
        ptr = ptr->next;
    }
    return count;
}

//Return number of values of specified item in the list
int LinkedList::count(int item){
    Node *ptr = head;
    int count = 0;

    while(ptr != nullptr) {
        if(ptr->data == item)
            count++;
        ptr = ptr->next;
    }
    return count;
}

//Remove item from list
void LinkedList::remove(int item){
    Node *pre = nullptr;
    Node *cur = head;

    while(cur != nullptr && cur->data != item)
    {
        pre = cur;
        cur = cur->next;
    }

    if(cur == nullptr)//If value not found in list
        return;

    if(cur == head)//If value is first in the list
        head = head->next;
    else
        pre->next = cur->next;
    delete cur;//Free memory allocated for the node
}

//Destructor
LinkedList::~LinkedList(){
    Node *ptr = head;
    while(ptr != nullptr){
        int item = ptr->data;
        ptr = ptr->next;
        remove(item);
    }
}

int main(){
    /*Create a list of integers*/
    LinkedList list;

    //Test add and addEnd
    list.add(3);
    list.add(2);
    list.add(1);
    list.addEnd(4);
    list.addEnd(5);
    list.addEnd(1);

    cout << "The list is: ";
    list.display();
    cout << endl << endl;

    //Test remove
    list.remove(3);
    list.remove(2);

    cout << "The list is: ";
    list.display();
    cout << endl << endl;

    //Test contains
    if(list.contains(5))
        cout << "List contains 5" << endl;
    else
        cout << "List does not contain 5" << endl;

    //Test count
    cout << "Number of values in the list: " << list.count() << endl;
    cout << "Number of 1's in the list: " << list.count(1) << endl;

    return 0;
}

OUTPUT:

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