HashTable

#include <iostream>
#include <string>
#include <utility>
#include <vector>

const int kHashParam = 17;
const int kModParam = 1000000007;

int Hash(const std::string& value) {
  int result = 0;
  for (const char c : value) {
    result = (result * kHashParam + c) % kModParam;
  }
  return result;
}

struct Node {
  std::string Value;
  Node* Next;
};

class HashTable {
 public:
  HashTable() : table(20, nullptr) {}
  ~HashTable() {/*TODO: clear*/}

  bool Has(const std::string& value) const {
    const int hash = Hash(value) % table.size();
    for (Node* p = table[hash]; p != nullptr; p = p->Next) {
      if (p->Value == value) return true;
    }
    return false;
  }

  bool Add(const std::string& value) {
    const int hash = Hash(value) % table.size();
    for (Node* p = table[hash]; p != nullptr; p = p->Next) {
      if (p->Value == value) return false;
    }
    table[hash] = new Node{value, table[hash]};
    return true;
  }

  bool Remove(const std::string& value) {
    const int hash = Hash(value) % table.size();
    Node* p = table[hash];
    if (p == nullptr) return false;
    if (p->Value == value) {
      table[hash] = p->Next;
      delete p;
      return true;
    }
    for (; p->Next != nullptr; p = p->Next) {
      if (p->Next->Value == value) {
        Node* tmp = p->Next;
        p->Next = p->Next->Next;
        delete tmp;
        return true;
      }
    }
    return false;
  }

 private:
  std::vector<Node*> table;
};

int main() {
  HashTable t;

  char command = 0;
  std::string value;
  while (std::cin >> command >> value) {
    if (command == '?') {
      std::cout << (t.Has(value) ? "OK" : "FAIL") << std::endl;
    } else if (command == '+') {
      std::cout << (t.Add(value) ? "OK" : "FAIL") << std::endl;
    } else if (command == '-') {
      std::cout << (t.Remove(value) ? "OK" : "FAIL") << std::endl;
    }
  }
  return 0;
}

#include <unordered_set>

int main1() {
  std::unordered_set<std::string> t;
  // В t будет использована std::hash<std::string>, имеющая реализацию в std.
  char command = 0;
  std::string value;
  while (std::cin >> command >> value) {
    if (command == '?') {
//      std::cout << (t.Has(value) ? "OK" : "FAIL") << std::endl;
    } else if (command == '+') {
//      std::cout << (t.Add(value) ? "OK" : "FAIL") << std::endl;
    } else if (command == '-') {
//      std::cout << (t.Remove(value) ? "OK" : "FAIL") << std::endl;
    }
  }
  return 0;
}