Randomly select an element from an array

Solution

#include <iostream>

#include <cstdlib>

#include <ctime>

using namespace std;

int rand_select_elems(int a[], int len)

{

srand((unsigned)time(NULL));

static int l = 0;

int n = rand() % (len - l);

int m = l + n;

int t = a[l];

a[l] = a[m];

a[m] = t;

t = a[l];

l ++;

l %= len;

return t;

}

int main(int argc, char* argv[])

{

int a[20];

for(int i = 0; i < 20; i++){

a[i] = i;

}

for(int i = 0; i < 50; i ++){

cout.width(2);

cout << i << " ";

}

for(int i = 0; i < 50; i ++){

cout.width(2);

cout << rand_select_elems(a, 20) << " ";

}

cout << endl;

return 0;

}

Output

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49

13 8 0 14 17 2 11 7 5 19 1 10 4 18 9 6 12 3 16 15 18 5 13 9 3 0 10 7 2 15 8 1 17 16 19 11 4 14 12 6 16 2 18 19 14 13 1 7 0 6