Linked list in C++

LinkedList.cpp

#include <iostream>




class IntNode {
    public:
        IntNode* next;
        int val;

        IntNode(int init) {
            val = init;
        }
};


class LinkedList {
    public:
        IntNode* first;
        
        LinkedList(int init) {
            first = new IntNode(init);
        }
        
        int get(int idx) {
            IntNode* node = first;
            for (int i = 0; i < idx; i++) {
                node = node->next;
            }
            return node->val;
        }
        
        void append(int value) {
            IntNode* node = first;
            while (node->next) {
                node = node->next;
            }
            node->next = new IntNode(value);
        }
        
        void index(int idx, int value) {
            IntNode* node = first;
            for (int i = 0; i < idx; i++) {
                node = node->next;
            }
            node->val = value;
        }
        
        void insert(int idx, int value) {
            // Get the node at index idx
            IntNode* node = first;
            int placeholder;
            for (int i = 0; i < idx; i++) {
                node = node->next;
            }
            placeholder = node->val;
            node->val = value;
            node = node->next;
            
            // Shift all of the nodes' values to the right
            while (node->next) {
                node->val = placeholder;
                node = node->next;
                placeholder = node->val;
            }
        }
        
        void del(int idx) {
            if (idx==0) {
                IntNode* placeholder = first;
                first = first->next;
                delete(placeholder);
                return;
            }

            IntNode* pnode;
            IntNode* node = first;
            for (int i = 0; i < idx; i++) {
                if (i == idx-1) pnode = node;
                node = node->next;
            }
            pnode->next = node->next;
            delete(node);
        }
        
        LinkedList slice(int idx1, int idx2) {
            LinkedList n(0);
            IntNode* node = first;
            for (int i = 0; i < idx2; i++) {
                if (i >= idx1) n.append(node->val);
                node = node->next;
            }
            n.del(0);
            return n;
        }
        
        int length() {
            int len = 1;
            IntNode* node = first;
            while (node->next) {
                node = node->next;
                len++;
            }
            return len;
        }
        
        void print() {
            IntNode* node = first;
            int i = 0;
            while (node->next) {
                std::cout << "Value at index: " << i++ << " = " << node->val << "\n";
                node = node->next;
            }
        }
};


int main() {
    LinkedList list(0);
    for (int i = 1; i < 10; i++) {
        list.append(i);
    }

    list.index(3, 666);
    list.insert(4, 667);
    list.del(3);
    
    list.print();
    list.slice(0, 3).print();
    
    
    std::cout << "Length of list = " << list.length() << "\n";
    std::cout << "Length of list = " << list.slice(0, 3).length() << "\n";

    return 0;
}