Random_Number_Selection_from_Array.cpp

//Randomly select a number from a set of numbers.
#include<bits/stdc++.h>

using namespace std;

int selectRandom(int x)
{
    static int res;    // The resultant random number
    static int count = 0;  //Count of numbers visited so far in stream

    count++;  // increment count of numbers seen so far

    // If this is the first element from stream, return it
    if (count == 1)
        res = x;
    else
    {
        // Generate a random number from 0 to count - 1
        int i = rand() % count;

        // Replace the prev random number with new number with 1/count probability
        if (i == count - 1)
            res  = x;
    }
    return res;
}

int main()
{

    int n;
    cout<<"Enter the Number of elements to be inserted in Array : ";
    cin >> n;

    int a[n];

    for (int i = 0; i < n; i++){
      cin>>a[i];
    }

    for (int i = 0; i < n; ++i)
        printf("Random number from first %d numbers is %d \n",i+1, selectRandom(a[i]));
    return 0;
}