SLList.cpp

#include <iostream>

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

  IntNode(int i, IntNode *n) {
    item = i;
    next = n;
  }
};

class SLList {
private:
  /** Pointer pointing to the first element in list. */
  // IntNode *first;

  /** Pointer pointing to the sentinel node. */
  IntNode *sentinel;

  /** Stores the current size of the list. */
  int count;

  /** Helper method that returns size recursively. */
  // int size(IntNode *p) const {
  //   if (p->next == nullptr)
  //     return 1;
  //   return 1 + size(p->next);
  // }

public:
  /** Construct a new SLList object. */
  SLList() {
    // first = nullptr;
    sentinel = new IntNode(63, nullptr);
    count = 0;
  }

  /** Construct a new SLList object with element x. */
  SLList(int x) {
    // first = new IntNode(x, nullptr);
    sentinel = new IntNode(63, nullptr);
    count = 0;
    addFirst(x);
  }

  /** Add x at the beginning of the list. */
  void addFirst(int x) {
    count += 1;
    // first = new IntNode(x, first);
    sentinel->next = new IntNode(x, sentinel->next);
  }

  /** Return the first element. */
  int &getFirst() {
    // return first->item;
    return sentinel->next->item;
  }

  /** Return the number of elements in list. */
  int size() const {
    return count;
    // return size(first);
  }

  /** Append the list with x. */
  void addLast(int x) {
    count += 1;

    // if (first == NULL) {
    //   first = new IntNode(x, NULL);
    //   return;
    // }

    // IntNode *p = first;
    IntNode *p = sentinel;
    while (p->next != nullptr) {
      p = p->next;
    }
    p->next = new IntNode(x, nullptr);
  }
};

int main() {
  SLList L(10);
  L.addFirst(5);
  L.addLast(15);
  std::cout << L.size() << std::endl;
  std::cout << L.getFirst() << std::endl;
}