Randil's math problem (C++ code)

#include <iostream>
#include <iomanip>
#include <ctime>
#include <random>
#include <cmath>

#define TRIES 5000


using namespace std;

int main()
{
    mt19937 mersenne(static_cast<unsigned int>(time(0)));

    for(int lo=1; lo<=18; lo++)
        for(int hi=lo+1;hi<=19;hi++){

            double pr=0.05*hi, pw=0.05*lo;
            double qr=1-pr, qw=1-pw;

            double agreen=log(pr/pw); //should be positive
            double ared=log(qr/qw); //should be negative

            int countsum=0;
            for(int temp=1;temp<=TRIES;temp++){

                unsigned int thenum=mersenne()%10000;
                unsigned int num[]={thenum/1000, (thenum/100)%10, (thenum/10)%10, thenum%10};

                int flags[10000]{};
                double logprobs[40]{};
                int countsgreen[40]{};
                int countsred[40]{};

                //first guess

                unsigned int theguess=mersenne()%10000;
                unsigned int guess[]={theguess/1000, (theguess/100)%10, (theguess/10)%10, theguess%10};


                int count=1;
                while(true){
                    //check if guess matches num
                    int check=1;
                    for(int i=0;i<4;i++)
                        if(guess[i]!=num[i]) {check=0; break;}
                    if(check==1){//match
                        break;
                    }

                    //no match

                    //add occurrences
                    for(int i=0;i<4;i++){
                        if(guess[i]==num[i]){
                            //green with prob pr, red with prob qr
                            if(((double) mersenne())/mersenne.max() < pr) //green
                                countsgreen[10*i+guess[i]]++;
                            else
                                countsred[10*i+guess[i]]++;
                        }
                        else{
                            //green with prob pw, red with prob qw
                            if(((double) mersenne())/mersenne.max() < pw) //green
                                countsgreen[10*i+guess[i]]++;
                            else
                                countsred[10*i+guess[i]]++;
                        }
                    }

                    //set flag so as to not guess it again
                    flags[theguess]=1;

                    //calculate normalized log likelihood for each digit
                    for(int i=0;i<40;i++)
                        logprobs[i]=agreen*countsgreen[i]+ared*countsred[i];

                    //find largest normalized log likelihood over all 4-digit numbers
                    //if ties, takes the first instance
                    double largest=-100000;
                    int lrg1=0,lrg2=0,lrg3=0,lrg4=0;
                    for(int i1=0;i1<10;i1++)
                        for(int i2=0;i2<10;i2++)
                            for(int i3=0;i3<10;i3++)
                                for(int i4=0;i4<10;i4++)
                                    if(!flags[1000*i1+100*i2+10*i3+i4]){
                                        double s=logprobs[i1]+logprobs[10+i2]+logprobs[20+i3]+logprobs[30+i4];
                                        if(s>largest){
                                            largest=s;
                                            lrg1=i1;
                                            lrg2=i2;
                                            lrg3=i3;
                                            lrg4=i4;
                                        }
                                    }


                    //next guess is lrg1 lrg2 lrg3 lrg4

                    guess[0]=lrg1;
                    guess[1]=lrg2;
                    guess[2]=lrg3;
                    guess[3]=lrg4;
                    theguess=1000*lrg1+100*lrg2+10*lrg3+lrg4;


                    count++;
                    if(count>=10002){
                        cout << "failed";
                        exit(1);
                    }


                }

                countsum+=count;
            }

            cout << fixed << setprecision(2) << "Average tries for pr=" << pr << " , pw=" << pw << ": " << ((double) countsum)/TRIES << endl;
        }
    return 0;
}