gistfile1.hpp

#include <iostream>
#include <string>
#include <sstream>
using namespace std;

#define DAYS_IN_YEAR 360	// In order to simplify the program
#define DAYS 30				// use 30 days in each month.
#define MONTHS 12			// This still gives a rough estimate on how
// well the hashing functions work.

int hash1(int month, int day);
int hash2(int month, int day);
string formatDate(int month, int day);

int main()
{
    // for hash1
    string year1[DAYS_IN_YEAR];
    // for hash2
    string year2[DAYS_IN_YEAR];
    int numOfDays = 0;
    int collisions1 = DAYS_IN_YEAR;
    int collisions2 = DAYS_IN_YEAR;

    // clear both arrays
    for ( int i = 0; i < DAYS_IN_YEAR; i++ )
        year1[i] = year2[i] = "";

    for ( int i = 1; i <= MONTHS; i++ ) {
        for ( int j = 1; j <= DAYS; j++ ) {
            year1[ hash1(i, j) ] = formatDate(i, j);
            year2[ hash2(i, j) ] = formatDate(i, j);
        }
    }

    // total collisions for hash1
    for ( int i = 0; i < DAYS_IN_YEAR; i++ ) {
        if ( year1[i] != "" )
            numOfDays += 1;
    }
    collisions1 -= numOfDays;

    numOfDays = 0;

    // total collisions for hash2
    for ( int i = 0; i < DAYS_IN_YEAR; i++ ) {
        if ( year2[i] != "" )
            numOfDays += 1;
    }
    collisions2 -= numOfDays;

    //for ( int i = 0; i < DAYS_IN_YEAR; i++ ) {
    //	cout << "index: " << i << '\t' << year1[i] << endl;

    cout << "hash1" << '\t' << "hash2" << endl
        << "-------" << '\t' << "-------" << endl
        << collisions1 << '\t' << collisions2 << endl;

    return 0;
}

int hash1(int month, int day)
{
    return ( ( month + (3 * day) ) % 101 );
}

int hash2(int month, int day)
{
    return ( ( day + ( 3 * month ) ) % 101 );
}

string formatDate(int month, int day)
{
    stringstream ss;
    ss << month << "/" << day;
    return ( ss.str() );
}