std :: vector를 섞는 방법?

std :: vector를 섞는 방법?

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std::vectorC ++에서 셔플하는 일반적인 재사용 가능한 방법을 찾고 있습니다. 이것이 내가 현재하는 방법이지만 중간 배열이 필요하고 항목 유형을 알아야하기 때문에 매우 효율적이지 않다고 생각합니다 (이 예에서는 DeckCard).

srand(time(NULL));

cards_.clear();

while (temp.size() > 0) {
    int idx = rand() % temp.size();
    DeckCard* card = temp[idx];
    cards_.push_back(card);
    temp.erase(temp.begin() + idx);
}

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C ++ 11부터는 다음을 선호해야합니다.

#include <algorithm>
#include <random>

auto rng = std::default_random_engine {};
std::shuffle(std::begin(cards_), std::end(cards_), rng);

Live example on Coliru

매번 다른 순열을 생성하려는 경우 rng여러 호출 에서 동일한 인스턴스를 재사용해야합니다 std::shuffle!

또한 프로그램이 실행될 때마다 다른 순서의 셔플을 생성하도록하려면 임의 엔진의 생성자에 std::random_device.

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C ++ 98의 경우 다음을 사용할 수 있습니다.

#include <algorithm>

std::random_shuffle(cards_.begin(), cards_.end());

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http://www.cplusplus.com/reference/algorithm/shuffle/

// shuffle algorithm example
#include <iostream>     // std::cout
#include <algorithm>    // std::shuffle
#include <vector>       // std::vector
#include <random>       // std::default_random_engine
#include <chrono>       // std::chrono::system_clock

int main () 
{
    // obtain a time-based seed:
    unsigned seed = std::chrono::system_clock::now().time_since_epoch().count();
    std::default_random_engine e(seed);

    while(true)
    {
      std::vector<int> foo{1,2,3,4,5};

      std::shuffle(foo.begin(), foo.end(), e);

      std::cout << "shuffled elements:";
      for (int& x: foo) std::cout << ' ' << x;
      std::cout << '\n';
    }

    return 0;
}

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@Cicada가 말한 것 외에도 먼저 씨를 뿌려야합니다.

srand(unsigned(time(NULL)));
std::random_shuffle(cards_.begin(), cards_.end());

@FredLarson의 의견에 따라 :

the source of randomness for this version of random_shuffle() is implementation defined, so it may not use rand() at all. Then srand() would have no effect.

So YMMV.

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If you are using boost you could use this class (debug_mode is set to false, if you want that the randomizing could be predictable beetween execution you have to set it to true):

#include <iostream>
#include <ctime>
#include <boost/random/mersenne_twister.hpp>
#include <boost/random/uniform_int.hpp>
#include <boost/random/uniform_int_distribution.hpp>
#include <boost/random/variate_generator.hpp>
#include <algorithm> // std::random_shuffle

using namespace std;
using namespace boost;

class Randomizer {
private:
    static const bool debug_mode = false;
    random::mt19937 rng_;

    // The private constructor so that the user can not directly instantiate
    Randomizer() {
        if(debug_mode==true){
            this->rng_ = random::mt19937();
        }else{
            this->rng_ = random::mt19937(current_time_nanoseconds());
        }
    };

    int current_time_nanoseconds(){
        struct timespec tm;
        clock_gettime(CLOCK_REALTIME, &tm);
        return tm.tv_nsec;
    }

    // C++ 03
    // ========
    // Dont forget to declare these two. You want to make sure they
    // are unacceptable otherwise you may accidentally get copies of
    // your singleton appearing.
    Randomizer(Randomizer const&);     // Don't Implement
    void operator=(Randomizer const&); // Don't implement

public:
    static Randomizer& get_instance(){
        // The only instance of the class is created at the first call get_instance ()
        // and will be destroyed only when the program exits
        static Randomizer instance;
        return instance;
    }

    template<typename RandomAccessIterator>
    void random_shuffle(RandomAccessIterator first, RandomAccessIterator last){
        boost::variate_generator<boost::mt19937&, boost::uniform_int<> > random_number_shuffler(rng_, boost::uniform_int<>());
        std::random_shuffle(first, last, random_number_shuffler);
    }

    int rand(unsigned int floor, unsigned int ceil){
        random::uniform_int_distribution<> rand_ = random::uniform_int_distribution<> (floor,ceil);
        return (rand_(rng_));
    }
};

Than you can test it with this code:

#include "Randomizer.h"
#include <iostream>
using namespace std;

int main (int argc, char* argv[]) {
    vector<int> v;
    v.push_back(1);v.push_back(2);v.push_back(3);v.push_back(4);v.push_back(5);
    v.push_back(6);v.push_back(7);v.push_back(8);v.push_back(9);v.push_back(10);

    Randomizer::get_instance().random_shuffle(v.begin(), v.end());
    for(unsigned int i=0; i<v.size(); i++){
        cout << v[i] << ", ";
    }
    return 0;
}

참고URL : https://stackoverflow.com/questions/6926433/how-to-shuffle-a-stdvector