Member Avatar for rfrapp

Hello, I am trying to fill an array with 20 unique random values between 1 and 60. I know what I need to do to get this to work, but I'm not sure how to do it. Here's what I've got:

void fillArray( int arr[], int size)
{
    int arr2[20];
    bool found[20] = {false};

    for (int i = 0; i < size; i++)
    {
        arr[i] = rand() % 60 + 1;
        arr2[i] = arr[i];

        for (int j = 0; j < size; j++) // check for duplicates in array
        {
            if (arr[i] == arr[j])
            {
                found[i] = true;
                arr[i] = rand() % 60 + 1;
            }
        }
    }
}

My program checks an array for duplicates, but doesn't check the duplicates to see if they themselves are duplicates. How might I go about doing that? Thank you for your time!

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Member Avatar for iamthwee

This question has been asked many many times before.

The idea is to use std::random_shuffle.

So populate an array with values 1 through to 60.

Then shuffle the indexs as many times as you wish ( this involves picking two elements and swapping them.)
When you've finished you should have an array of random values ranging from 1-60.

Edited by iamthwee
Member Avatar for WaltP 
Set up an array with the values 1-MAX (array[MAX], MAX being 60)
set up a loop with index 1 to 20
    get random number from 0 to MAX-index
    use that number as index into array to store the next number
    loop from MAX-index to MAX-2 and shuffle all contents down 1 entry
Member Avatar for Despairy

Not sure if it's just because I just woke up, but a few questions:
1. What is arr2 for?
2. Do you think the inner loop should really go all the way to the end? i don't :P

maybe you could leave the inner loop out.
make a boolean boolArray[SIZE=60] ( reset to false ) and perform a while loop

lets say you started looping , and randomized a number.
now check if boolArray[randomizedNumber] = false then you havent used this number
and can use it in the array[currentPlace] and you can move the currentPlace++.
(don't forget to update the boolean array)
and if it is true just don't go into the IF statement and the loop will just rendomize
a new Value.

hope I didn't help too much :O

Edited by Reverend Jim because: Fixed formatting
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