Randomness

//Based on refutation to given solution to Riddler Express at http://fivethirtyeight.com/features/dont-throw-out-that-calendar/#ss-1

//sample output:
/*
Games played: 2000000
Games won: 32271
Proportion: 0.0161355
Games played: 2000000
Games won: 32377
Proportion: 0.0161885
Games played: 2000000
Games won: 32272
Proportion: 0.016136
Games played: 2000000
Games won: 32450
Proportion: 0.016225
Games played: 2000000
Games won: 32500
Proportion: 0.01625
Games played: 2000000
Games won: 32304
Proportion: 0.016152
Games played: 2000000
Games won: 32554
Proportion: 0.016277
Games played: 2000000
Games won: 32548
Proportion: 0.016274
Games played: 2000000
Games won: 32682
Proportion: 0.016341
Games played: 2000000
Games won: 32466
Proportion: 0.016233
Total games played: 20000000
Total games won: 324424
Proportion: 0.0162212
*/

#include <random>
#include <iostream>
#include <sstream>
#include <chrono>

#define LIMIT 2000000
#define REPEATS 10

//std::random_device rd;
unsigned seed = static_cast<int> (std::chrono::system_clock::now().time_since_epoch().count());


std::mt19937 rval(seed);

int main(int argc, char** argv)
{
    int deck[52];


    int totalwins=0;
    for(int kk=0;kk<REPEATS;kk++)
    {

        int countwin=0;

        for(int k=0;k<LIMIT;k++)
        {

            for(int i=0;i<52;i++) deck[i]=-1;

            for(int i=51;i>=0;i--)
            {
                unsigned int j=rval()%(i+1);

                int pos=0;
                while(j>0 || deck[pos]>=0)
                {
                    if(deck[pos]>=0) pos++;
                    else {pos++; j--;}
                }
                deck[pos]=i;

            }

            //flip over card; do not match with position mod 13

            int win=1;
            for(int i=0;i<52;i++)
                if(deck[i]%13==i%13) win=0;

            if(win==1) countwin++;
        }

        std::cout << "\nGames played: " << LIMIT << "\nGames won: " << countwin << "\nProportion: " << (double)countwin/LIMIT;
        totalwins+=countwin;
    }

    std::cout << "\nTotal games played: " << LIMIT*REPEATS << "\nTotal games won: " << totalwins << "\nProportion: " << (double)totalwins/(LIMIT*REPEATS);

}