C ++ list :: sort的自定义比较函数 [英] C++ Custom compare function for list::sort

问题描述

您好我无法编译一段简单的代码。我创建一个类实现一个卡片，我想使用list :: short方法创建一个shuffle方法。

Hi I'm having trouble compiling a simple piece of code. I am creating a class which implements a Deck of cards, and I want to create a shuffle method using the list::short method.

相关代码：

deck.h

#ifndef _DECK_H
#define _DECK_H

#include <list>
#include <ostream>

#include "Card.h"
#include "RandomGenerator.h"

using namespace std;

class Deck {
private:
    static const int CARD_NUMBER = Card::CARDS_PER_SUIT*Card::SUIT_NUMBER;
    list<Card *> *cards;
    RandomGenerator rg;

public:
    Deck();
    ~Deck();
    void shuffle();
private:
    bool const compareRandom(const Card *a, const Card *b);

};

#endif  /* _DECK_H */

deck.cc： p>

deck.cc:

#include "Deck.h"

/**
 * Fills the deck with a set of 52 cards
 */
Deck::Deck() {
    cards = new list<Card *>();
    for(int i = 0; i < CARD_NUMBER; i++)
        cards->push_back(
                new Card(
                    Card::Suit(int(i/Card::CARDS_PER_SUIT)),
                    i%Card::CARDS_PER_SUIT)
        );
}

Deck::~Deck() {
    gather();
    for(list<Card *>::iterator c = cards->begin(); c != cards->end(); c++)
        delete *c;
    delete cards;
}

bool const Deck::compareRandom(const Card *a, const Card *b) {
    return rg.randomBool();
}

void Deck::shuffle() {
    cards->sort(compareRandom);
}

$ b <

The compiler shows the next message (ignore line numbers):

Deck.cc: In member function ‘void Deck::shuffle()’:
Deck.cc:66: error: no matching function for call to ‘std::list<Card*, std::allocator<Card*> >::sort(<unresolved overloaded function type>)’
/usr/include/c++/4.3/bits/list.tcc:303: note: candidates are: void std::list<_Tp, _Alloc>::sort() [with _Tp = Card*, _Alloc = std::allocator<Card*>]
/usr/include/c++/4.3/bits/list.tcc:380: note:                 void std::list<_Tp, _Alloc>::sort(_StrictWeakOrdering) [with _StrictWeakOrdering = const bool (Deck::*)(const Card*, const Card*), _Tp = Card*, _Alloc = std::allocator<Card*>]

问题必须在compareRandom引用上，无法找到搜索此问题的答案。

The problem has to be on the compareRandom reference that I'm not using correctly, I cant find googling the answer to this problem.

提前感谢。

推荐答案

我可以说什么：）

首先，不要存储指向 Card 卡直接在容器中。如果您坚持存储任何原因的指针，请使用 Boost 中的 shared_ptr< Card> 。第二，你可以使用 std :: random_shuffle ，并将随机数生成器传递给它，而不是实现你的shuffle功能。

First, don't store a pointer to Card, just store the cards directly in the container. If you insist on storing pointers to them for any reason, use shared_ptr<Card> from Boost. Second, you can use std::random_shuffle and pass your random-number-generator to it instead of implementing your your shuffle function.

---

我可以再说一遍：）

这是我的想法，除非你不得不使用 list 因为任何原因，虽然我不请参阅原因。

This is what I have in mind, unless you have to use list for whatever reason, although I don't see that reason.

#include <iostream>
#include <vector>
#include <deque>
#include <algorithm>

class Card
{
// ...
};

int main()
{
    typedef std::vector<Card> Deck;
    Deck deck;

    // ... fill deck with cards.

    // There is an optional third parameter,
    // if you need to pass YOUR random-number-generator!
    // If you do, I recommend Boost implementation.
    std::random_shuffle(deck.begin(), deck.end());
}

我喜欢直接在 / code>，虽然你可能不喜欢它。另外，如果你看到 std :: vector 在你的情况下有性能问题，你可以用 std :: deque ：

I like to deal with containers directly in C++, though you may not like it. Also, if you see that std::vector has performance issues in your case, you could just replace the typedef with std::deque:

typedef std::deque<Card> Deck;

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