Question

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How exactly should I implement a shuffle or random-number algorithm for an array to display quotes in random order?

I have a small array that I need the values to be randomly shuffled around within the array. I can do this in python using random.shuffle(), but I can seem to figure out how to do it in C++.

Here is an example in python of what I want to do in C++

#!/usr/bin/python

import random

array = [1,2,3,4,5]

random.shuffle(array)

print array

Answer 1

You can use std::random_shuffle from <algorithm>.

Here’s a basic example from the page:

#include <algorithm>                                                                                                    
#include <vector>                                                                                                       
#include <iostream>                                                                                                     
#include <iterator>                                                                                                     

int main()                                                                                                              
{                                                                                                                       
   const int SIZE=10;

   // create and initialize an array                                                                                                   
   int arr[] = {1,2,3,4,5,6,7,8,9,10};                                                                                  

   std::random_shuffle(arr, arr+SIZE);      

   // copy the contents of the array to output                                                                            
   std::copy(arr, arr+SIZE, std::ostream_iterator<int>(std::cout, " "));                                                
   std::cout << std::endl;                                                                                              

   // shuffling an std:: container, here it's std::vector                                                                                         
   std::vector<int> ivec(arr, arr+SIZE);                                                                                
   std::random_shuffle(ivec.begin(), ivec.end());                                                                       
   std::copy(ivec.begin(), ivec.end(), std::ostream_iterator<int>(std::cout, " "));                                     
}        

You can do it with anything that uses random access iterators, like std::vector or std::deque or just a plain array like above.