monte carlo birthday problem java code example

Example: monte carlo birthday problem java

#include <stdio.h>        // print
#include <stdlib.h>   <span                data-mce-type="bookmark"                id="mce_SELREST_start"              data-mce-style="overflow:hidden;line-height:0"              style="overflow:hidden;line-height:0"           ></span>   // rand
#include <time.h>     // time
 
// This program will determine the percentage of times that two or more people share a birthday
// It will iterate from 2 people to 'maxNumPeople' and in each version it will do 'numSimulations' simulations
int main()
{
    int numPeople;                  // Number of people in this version
    int maxNumPeople = 100;         // Maximum number of people to test with. Must be less than 100
    int simNum;                     // Simulation number
    long numSimulations = 1000000;  // Number of simulations to try in this version
    long numMatches;                // Keeps track of number of matches in this version
    int birthdays[100];
    int i, j;                       // Incrementers fin for loop
    int isMatch;                    // Flag for later
 
    // Seed RNG with time to get unique results each time
    srand(time(NULL));
 
    // Iterate over the number of people in this version
    for(numPeople=2; numPeople<maxNumPeople; numPeople++)
    {
        // Reset the number of matchs for this version
        numMatches = 0;
 
        // Iterate the number of simulations in this version
        for(simNum = 0; simNum<numSimulations; simNum++)
        {
            for(i=0; i<numPeople; i++)
            {
                // Give each bday a value, in this case a day from 1 to 365 inclusive
                // rand()%365 returns from 0 to 364 so we add 1 to it
                // We could just as easily leave the 1 off and it would still work, but doesn't hurt
                birthdays[i] = 1 + rand()%365;
            }
 
            // Reset the isMatch flag
            isMatch=0; 
 
            // Determine if there is a match
            // Note that this is a very inefficent way to do compare
            for(i=0; i<numPeople-1; i++)
            {
                for(j=i+1; j<span                data-mce-type="bookmark"                id="mce_SELREST_start"              data-mce-style="overflow:hidden;line-height:0"              style="overflow:hidden;line-height:0"           ></span><numPeople; j++)
                {
                    // Compare i and j birthdays
                    if(birthdays[i] == birthdays[j])
                    {
                        // If they match, then set flag and break
                        isMatch=1;
                        break;
                    }
                }
 
                // This flag is to break out of the outer for loop if a mathc is already found
                if(isMatch==1)
                {
                    break;
                }
            }
 
            // If the match flag was set, increment the number of matches
            if(isMatch==1)
                numMatches++;
 
        }
 
        // Print out the numPeople in this version and the percentage of times there wa a match
        printf("%d, %f \n", numPeople, 100.0*numMatches/numSimulations);
    }
 
    return 0;
}