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;
}