/* Due date for this lab: Saturday 11/5 */ 
/* Please email me your code using the following command  */
/* mail -s "CISC2100 lab2" xzhang@fordham.edu < hash.cpp */
/* Extra credit part 
 *   Create a real hash table by making each table entry a 
 *     list of words, you can use STL list container: 
 *
 *   list<string>  table[TABLE_SIZE];                                     
 *
 *   and store the words in the list. 
 *   See this tutorial: http://www.yolinux.com/TUTORIALS/LinuxTutorialC++STL.html#LIST */
#include <iostream>
#include <fstream>

using namespace std;

/* In this program, we explore the idea of hashing function
 * that takes a string input, and returns an integer value
 * between 0...hashTableSize-1
 * Application: 
 *  1. hash table (a data structure) that has O(1) search performance 
 *  2. to store a set of words (or other objects).  
 */

//The size of the hashtable... 
const int TABLE_SIZE=200;

/* Our hash function: 
 * precondition: hashTableSize>=2 
 * postcondition: return value is between 0, hashTableSize-1
 */
int MyHashFunction(string input, int hashTableSize)
{
 //TODO by you, does this functio implements a function (in mathematical sense)? //  What's the domain? What's the codomain? What's the range? 
 //
 // right now return 0 
 return 0;
}

/* read a set of words from file and initilze the hashtable 
 */ 
void InitTable (string fileName, int table [], int tableSize)
{
  ifstream file;
  int hashcode;
  string word;

  //Init table entries to be 0 
  for (int i=0;i<tableSize;i++)
	table[i]=0;
  
  //open file to read
  file.open (fileName);
  if (file.fail())
  {
	cout <<"File cannot be opened\n";
	return;
  } 

 
  bool endOfFile=false;
  //repeat until reach end of file
  do {
     //  1. read a word
     file >> word;
     
     if (!file.eof()) 
     {
  	//  2. Calcuate hashcode of the word using MyHashFunction

     	hashcode = MyHashFunction (word, tableSize);

      	table[hashcode]++; //one more word hashed to this code...  
     } 
     else
	endOfFile = true;
   } while (!endOfFile);
  
  //close the file 
  file.close();
}


int main()
{
    int hashTable[TABLE_SIZE]; //hashTable[i] is the number of words that 
		// are hashd to i 
    string word;
    char cont;

    InitTable ("wordsInAnimalFarm.txt", hashTable, TABLE_SIZE);

   //Todo: write some code to answer the follow questions.
   //Is MyHashFunction a one-to-one function from the words in "wordsInAnimalFarm.txt"
   // to 0...TABLE_SIZE-1
  
   // Is it onto? 

    cout <<"Check whether a word appears in the book Animal Farm\n";
    do {
      cout <<"Enter a word:";
      cin >> word;

      int hashCode = MyHashFunction (word, TABLE_SIZE);

      if (hashTable[hashCode]==0)
	cout <<"not in the book!\n"; //no word in dictionary is hased to to this hashcode 
      else
	cout <<"may in the book, but false positive is possible..."; 

      cout <<"Try again (y/n)?";
      cin >> cont;

    } while (cont=='y' || cont=='Y');
}