linkedList.cpp

#include <iostream>
#include <string>
using namespace std;

class Node {
public:
    int data;
    Node* next;
    Node(int val) {
        data = val;
        next = NULL;
    }    
};

class List{
    Node* head;
    Node* tail;
public:
    List() {
        head = tail = NULL;
    }

    void push_front(int val) {
        Node* newNode = new Node(val);

        if(head == NULL) {
            head = tail = newNode;
        } else {
            newNode->next = head;
            head = newNode;
        }
    }

    void push_back(int val) {
        Node* newNode = new Node(val);

        if(head == NULL) {
            head = tail = newNode;
        } else {
            tail->next = newNode;
            tail = newNode;
        }
    }

    void pop_front() {
        if(head == NULL) {
            return;
        } else if(head == tail) {
            delete head;
            head = tail = NULL;
        } else {
            Node* temp = head;
            head = head->next;
            temp->next = NULL;

            delete temp;
        }
    }

    void pop_back() {
        if(head == NULL) {
            return;
        } else if(head == tail) {
            delete head;
            head = tail = NULL;
        } else {
            Node* temp = head;
            while(temp->next != tail) {
                temp = temp->next;
            }
            temp->next = NULL;
            delete tail;
            tail = temp;
        }
    }

    void insert(int pos, int val) {
        if(pos < 0) {
            return;
        }

        if(pos == 0) {
            push_front(val);
            return;
        }
        
        Node* temp = head;
        for(int i = 0; i < pos-1; i++) {
            if(temp == NULL) {
                return;
            }
            temp = temp->next;
        }

        Node* newNode = new Node(val);
        newNode->next = temp->next;
        temp->next = newNode;
        
    }

    void printLL() {
        Node* temp = head;
        while(temp != NULL) {
            cout << temp->data << " " << "->" << " ";
            temp = temp->next;
        }
        cout << "NULL" << endl;
    }

    int search(int key) {
        Node* temp = head;
        int idx = 0;

        while(temp != NULL) {
            if(temp->data == key) {
                return idx;
            }
            temp = temp->next;
            idx++;
        }

        return -1;
    }
};

int main() {
    List ll;
    // ll.push_front(1);
    // ll.push_front(2);
    // ll.push_front(3); 

    // ll.push_back(4);

    // ll.pop_front();

    // ll.printLL();

    // ll.pop_back();

    ll.push_front(3);
    ll.push_front(2);
    ll.push_front(1); 

    ll.insert(1, 4);

    ll.printLL();

    cout << ll.search(4) << endl;

    return 0;
}