How To Shuffle Number In C++

Asked Nov 06 '16 at 10:30

Active Nov 06 '16 at 10:43

Viewed 39 times

I have number form 1-42 I want to let C++ shuffle number for me, I have number form 1-42 and I used code below :

#include <iostream>
#include <algorithm>

using namespace std;
int main()
{
int S[42]={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};
random_shuffle(&S[1], &S[42]);
cout<<S[42];
}

It's working, but the problem is every times i run it, it always show number 3 all the time, I think there is something wrong, Please help;

edited Nov 06 '16 at 10:43

Deduplicator

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asked Nov 06 '16 at 10:30

Hengly

3

Call `std::srand`, or better yet don't use `random_shuffle` if you have access to c++11 and beyond. – StoryTeller - Unslander Monica Nov 06 '16 at 10:31
don't you have to initialize random differently ? random generators always yield the same sequence at the start of the program unless you initialize it with system time for instance. – Jean-François Fabre Nov 06 '16 at 10:34
@StoryTeller Better not depend on `std::rand()`, nor `std::random_shuffle` using `std::rand()`. `std::shuffle` with a RNG from [``](http://en.cppreference.com/w/cpp/header/random) is superior. – Deduplicator Nov 06 '16 at 10:37
@Hengly, consider googling about it. You need to provide a seed to the random number generator, and if you provide the same seed every time, you'd get the same results. – StoryTeller - Unslander Monica Nov 06 '16 at 10:39
Seeding for RNG from ``: http://codereview.stackexchange.com/questions/109260/seed-stdmt19937-from-stdrandom-device – Deduplicator Nov 06 '16 at 10:42
1

BTW: `cout< – Deduplicator Nov 06 '16 at 10:44
Well, thank for replying, at that time I was a beginner at C++. – Hengly Jun 13 '17 at 14:43
I came back again to see this post, It reminds of how stupid I was, but anyway it was fun, guys! – Hengly Jul 27 '18 at 08:23

How To Shuffle Number In C++

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