generating random unique numbers

[jper]

so im basically new at c++.
i need to generate 20 entries randomly from 1-20, and each number must be unique.
i was able to generate the number but i don't know how to make them unique.
any suggestions?

#include <iostream>
#include <stdlib.h>
#include <time.h>
#include <math.h>

using namespace std;

int array[20];

int main ()
{
    srand(time(NULL));
    for (int i=0; i<20; i++)
    {
        int x;
        x=rand()%20+1;
        cout << array[0]<<x<< " ";
    }
    return 0;
}

[raptr_dflo]

Try putting the numbers 1-20 into your array first (in order), and then shuffling it. (Hint: start by picking a random element-index and swapping that element with the last element in the array, now you have only 19 more elements to deal with, etc.)

[NathanOliver]

If you can use STL then you could use the random shuffle algo. Since I don't think you can use that algo you would need to use two for loops. One to populate the array with the numbers 1-20 and the other to swap the elements in the array around. When you shuffle the element around go through the array for each element swap it with a random index in the array.

[jper]

If you can use STL then you could use the random shuffle algo. Since I don't think you can use that algo you would need to use two for loops. One to populate the array with the numbers 1-20 and the other to swap the elements in the array around. When you shuffle the element around go through the array for each element swap it with a random index in the array.

thanks nathan, i can't use STL but i'll do by creating two loops.thanks.