linkedlst.h

#ifndef LINKED_LIST_PROBLEM
#define LINKED_LIST_PROBLEM
#include <algorithm>
#include <fstream>
#include <iostream>
#include <set>
#include <vector>
using namespace std;
class SinglyLinkedListNode {
public:
  int data;
  SinglyLinkedListNode *next;

  SinglyLinkedListNode(int node_data) {
    this->data = node_data;
    this->next = nullptr;
  }
};

class SinglyLinkedList {
public:
  SinglyLinkedListNode *head;
  SinglyLinkedListNode *tail;

  SinglyLinkedList() {
    this->head = nullptr;
    this->tail = nullptr;
  }
  void insert_node(int node_data) {
    SinglyLinkedListNode *node = new SinglyLinkedListNode(node_data);
    if (!this->head)
      this->head = node;
    else
      this->tail->next = node;
    this->tail = node;
  }
};

void print_singly_linked_list(SinglyLinkedListNode *node, string sep,
                              ofstream &fout) {
  while (node) {
    fout << node->data;
    node = node->next;
    if (node)
      fout << sep;
  }
}
SinglyLinkedListNode *reverse(SinglyLinkedListNode *llist) {
  vector<int> temp;
  SinglyLinkedList *ls = new SinglyLinkedList();
  while (llist) {
    temp.push_back(llist->data);
    llist = llist->next;
  }
  auto rbegin = temp.rbegin();
  auto rend = temp.rend();
  while (rbegin != rend) {
    ls->insert_node(*rbegin);
    ++rbegin;
  }
}
SinglyLinkedListNode *mergeLists(SinglyLinkedListNode *head1,
                                 SinglyLinkedListNode *head2) {
  vector<int> temp;
  while (head1) {
    temp.push_back(head1->data);
    head1 = head1->next;
  }
  while (head2) {
    temp.push_back(head2->data);
    head2 = head2->next;
  }
  std::sort(temp.begin(), temp.end());
  SinglyLinkedList *it = new SinglyLinkedList();
  auto begin = temp.begin();
  auto end = temp.end();
  while (begin != end) {
    it->insert_node(*begin);
    ++begin;
  }
  return it->head;
}
#endif // !LINKED_LIST_PROBLEM