don't get random numbers every time

[liljr415]

This is my program i have to choose for random number between 1-25 and display them the program works perfectly just that every time i run its always the same numbers. I still haven't learned about crime so I'm trying to avoid since the professor said to use only what we know. I saw in the book that they used stand(99) but it doesn't work in my case. Any help is appreciated thank you.

#include <iostream>
#include <cstdlib> // include library to use rand

using namespace std;

int main(){
    int winner1;        // declare variables
    int winner2;
    int winner3;
    int winner4;
    bool same= true;

    
    
    while(same==true){   // while statement that will run if at least two random numbers are the same
        srand(99);
     winner1= rand() % 26;
     winner2= rand() % 26;
     winner3= rand() % 26;
     winner4= rand() % 26;
        
        
        if( winner1==winner2 || winner1==winner3 || winner1==winner4 || winner2==winner3 || winner2==winner4 || winner3==winner4)
            same=true;
        else                    // will exit loop when all four random numbers are different
            same=false;
    }
    
    cout << "The winning numbers are: " << winner1 <<", " << winner2 << ", " << winner3 << ", " << winner4 <<endl;
    // display the winning numbers
    return 0;
}

[Stewbond]

When you seed srand, the _sudorandom number generator will give a specific sequence of numbers based on that seed.

1) Seed the numbers only once. Do that at the start of main(). This way, winner1-4 will be different for each iteration of the while loop (currently they are always the same).

2) Seed with something like srand( time(NULL) );. This will seed the random number generator with a different number each time (because it's never the same value twice unless you're calling it in the same second).

[giblit]

unless you're calling it in the same second

Well time returns the number of milliseconds from midnight...

Also as mentioned rand is a pseudo random number generator which means its actually a sequence of numbers based off the starting seed the formula will look something along the lines to:

x0 = seed, P1 = some_intial_value , P2 = some_inital_value,
xn+1 = (P1 * xn + P2) % n

[TwilightSpectre]

@giblit

The value returned generally represents the number of seconds since 00:00 hours, Jan 1, 1970 UTC (i.e., the current unix timestamp)

http://www.cplusplus.com/reference/ctime/time/