Go4Expert - random generator for unique numbers

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random generator for unique numbers

Hi
I have an issue ,trying to build a unique number generator.
Specifiacally, the generator is this

Code:

                Random randomPerson=new Random(System.nanoTime());

                int no_persons=persons.length;

                

                int cnt=0;

                while(cnt<70) {

                        int person=randomPerson.nextInt(no_persons);

                        if(function()) {

                                cnt++;}

function() returns a boolean whether the random number hasn't used before (and some other operations eg insertion to an array)
When this program is executed, I either take the aprropriate output, or the program stucks (infinite loop). Is there any possibility to fix this infinite loop?

Thanks in advace!

Re: random generator for unique numbers

Presumably you mean something like this:

Code:

bool is_unique( int n) {

    // check array

}



int get_unique_person() {

    Random randomPerson = new Random( System.nanoTime());

    int no_persons = persons.length;

    int max_tries = 70;

    int cnt, person;



    for( cnt = 0; cnt < max_tries; ++cnt) {

        person = randomPerson.nextInt( no_persons);

        if( is_unique( person)) break;  // exit loop if it IS unique

    }

    if( cnt == max_tries) { // No unique number found in max_tries.

        // Deal with it....

    }

    return person;

}

If the range of your random numbers is relatively small, and particularly if you need to use most or all of them, then a better solution might be to create your own class called RndUnique that would contain a shuffled array of the integers in the range and return them one at a time.

Re: random generator for unique numbers