linked_list.cpp

#include <bits/stdc++.h>
using namespace std;

#define rep(i, l, r) for (int i = l; i < r; i++)
#define rrep(i, r, l) for (int i = r-1; i >=0; i--)
#define ll long long
#define nline '\n'
#define prn cout << "NO" << nline
#define pry cout << "YES" << nline
#define vi vector<int>
#define vvi vector<vi>
#define eb emplace_back
#define all(a) (a).begin(), (a).end()
#define rall(a) (a).rbegin(), (a).rend()
#define inparr(v)   \
  for (auto &x : v) \
    cin >> x;
#define pii pair<int, int>
#define pll pair<ll, ll>
#define vpii vector<pii>
#define vvpii vector<vector<pii>>
#define mp make_pair
#define ff first
#define ss second
#define float long double

// #define int long long

//---- Debugger ---- //
#ifdef LOCAL
#define debarr(a,n) cout<<#a<<" : ";for(int i=0;i<n;i++) cerr<<a[i]<<" "; cerr<<nline;
#define debmat(mat,row,col) cout<<#mat<<" :\n";for(int i=0;i<row;i++) {for(int j=0;j<col;j++) cerr<<mat[i][j]<<" ";cerr<<nline;}
#define pr(...) dbs(#__VA_ARGS__, __VA_ARGS__)
template <class S, class T>ostream& operator <<(ostream& os, const pair<S, T>& p) {return os << "(" << p.first << ", " << p.second << ")";}
template <class T>ostream& operator <<(ostream& os, const vector<T>& p) {os << "[ "; for (auto& it : p) os << it << " "; return os << "]";}
template <class T>ostream& operator <<(ostream& os, const unordered_set<T>& p) {os << "[ "; for (auto& it : p) os << it << " "; return os << "]";}
template <class S, class T>ostream& operator <<(ostream& os, const unordered_map<S, T>& p) {os << "[ "; for (auto& it : p) os << it << " "; return os << "]";}
template <class T>ostream& operator <<(ostream& os, const set<T>& p) {os << "[ "; for (auto& it : p) os << it << " "; return os << "]";}
template <class T>ostream& operator <<(ostream& os, const multiset<T>& p) {os << "[ "; for (auto& it : p) os << it << " "; return os << "]";}
template <class S, class T>ostream& operator <<(ostream& os, const map<S, T>& p) {os << "[ "; for (auto& it : p) os << it << " "; return os << "]";}
template <class T> void dbs(string str, T t) {cerr << str << " : " << t << "\n";}
template <class T, class... S> void dbs(string str, T t, S... s) {int idx = str.find(','); cerr << str.substr(0, idx) << " : " << t << ","; dbs(str.substr(idx + 1), s...);}
template <class T> void prc(T a, T b) {cerr << "["; for (T i = a; i != b; ++i) {if (i != a) cerr << ", "; cerr << *i;} cerr << "]\n";}
#else
#define pr(...)
#endif
//----------------- //

const int MOD = 1e9 + 7;
const int INF = 1e9 + 1;
class Node {
public:
    int data;
    Node* next;

    Node(int val) {
        data = val;
        next = nullptr;
    }
};

class MyLinkedList {
private:
    Node* head;
    Node* tail;
public:
    MyLinkedList() {
        head = tail = nullptr;
    }
    
    int get(int index) {
        int ans = -1;
        Node* curr = head;
        while(index-- && curr != nullptr) {
            curr = curr->next;
        }
        if(curr != nullptr) ans = curr->data;
        return ans;
    }
    
    void addAtHead(int val) {
        Node* newNode = new Node(val);
        if(head == nullptr) {
            head = tail = newNode;
            return;
        }
        newNode->next = head;
        head = newNode;
    }
    
    void addAtTail(int val) {
        Node* newNode = new Node(val);
        if(head == nullptr) {
            head = tail = newNode;
            return;
        }
        tail->next = newNode;
        newNode = tail;
    }

    // 1->2
    void addAtIndex(int index, int val) {
        Node* curr = head;
        Node* prev = head;
        Node* newNode = new Node(val);
        while(index-- && curr != nullptr) {
            prev = curr;
            curr = curr->next;
        }
        if(index == 0) {
            if(head == nullptr) head = newNode;
            else if(curr == head) {
                newNode->next = head;
                head = newNode;
            } else if(curr == nullptr) {
                prev->next = newNode;
                tail = newNode;
            } else {
                prev->next = newNode;
                newNode->next = curr;
            }
        }
    }
/*
The 5 Golden Rules of Raw Pointers

1. The "Empty Railyard" Rule (head == nullptr)

2. The Conductor Rule (Head Check)

3. The Caboose Rule (Tail Check)

4. The "Lone Car" Rule (head == tail)

5. The Connection Rule (New to Old, Old to New)
*/
    void deleteAtIndex(int index) {
        Node* curr = head;
        Node* prev = head;
        while(index-- && curr != nullptr) {
            prev = curr;
            curr = curr->next;
        }
        if(index == 0) {
            if(head == nullptr) return;
            if(curr == head) {

            }
        }
    }
};

/**
 * Your MyLinkedList object will be instantiated and called as such:
 * MyLinkedList* obj = new MyLinkedList();
 * int param_1 = obj->get(index);
 * obj->addAtHead(val);
 * obj->addAtTail(val);
 * obj->addAtIndex(index,val);
 * obj->deleteAtIndex(index);
 */
void solve() {
    // LinkedList list;
    // list.push_back(10);
    // list.push_front(20);
    // list.printLinkedList();

}

signed main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  int t = 1;
  // cin >> t;
  while (t--)
    solve();
}