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Poker probability

nigel (1)
I am just calculating the probablity of a straight and a flush. The proggramme should deal 5 random cards, 1 million times, checking for a flush and straight each time. Then at the end the divide the number of each by a million to get the percentage probablity.

I should be getting Flush=0.367%, Straight=0.76%. Instead I get .2%,.1% respectively. My code is shitty but if anyone could see where i made a mistake it would be very helpfull

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#include<iostream>
using namespace std;
const int size = 5;
void sort(int deck[],const int size);
void Flush(int deck[],double& flush,const int size);
void Straight(int deck[], double& straight,const int size);

int main()
{
   int deck[52],i,n,w;
   double flush=0,straight=0;

      for(i=0;i<52;i++)
       deck[i]=i;
      //initialise with values 0-51 to deck. 0=ace,1=1,2=2......

     for(w=0;w<1000000;w++)
         //repeat deal 1000000 times
   {
     for(n=0;n<size;n++)
            //deal the 5 cards
   {

     deck[n]=rand()%52;
     
   }
   
   Flush(deck,flush,size);
   Straight(deck,straight,size);
   // call the functions to count flushes and straights
   }

  flush=flush/10000;
   straight=straight/10;
  cout<<"Straight: "<<straight<<"%"<<endl<<"Flush:  "<<flush<<"%"<<endl;
        //print
 
   return 0;

}

void sort (int deck[],const int size)//bubble sort
{
   int temp,i,j;
   for(i=0;i<size;i++)
   {

       for(j=0;j<size-1-i;j++)
       {
           if (deck[j]<deck[j+1])
           {

               temp=deck[j];
               deck[j]=deck[j+1];
               deck[j+1]=temp;
           }
       }
   }

}

void Flush (int deck[],double& flush,const int size)
{
  int F_deck[5];//so not to change the array for next function
   for(int i=0;i<size;i++)
   {
       F_deck[i]=(deck[i]/13);
       //get suit

   }
   for(int j=0;j<size-1;j++)
   {
       if(F_deck[j]!=F_deck[j+1])
           return;
    //check if suits are equal
   }

   flush=flush+1;
}

void Straight(int deck[], double& straight,const int size)
{


   for(int i=0;i<size;i++)
   {

       deck[i]=((deck[i]%13));
    // give card value 0-12


   }
   sort(deck,size);
   //puts in order
 
   if((deck[0]-deck[1])!=1)
   return;
   if((deck[1]-deck[2])!=1)
   return;
   if((deck[2]-deck[3])!=1)
       return;
   if(((deck[3]-deck[4])==1)||((deck[3]-deck[4])==9)) //high low ace
       {
               straight++;
               
       }
       else
       return;
       }
jsmith (5804)
Yes, your deal algorithm allows you to deal out the same card twice (or more).

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for(n=0;n<size;n++)   //deal the 5 cards
     deck[n]=rand()%52;


Nothing stops deck[0] and deck[1] from both being set to, say, 42.

The simplest solution to your problem is to use std::random_shuffle on deck
instead of that for loop and then just pick the first five elements from the deck.
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