《Cracking the Coding Interview》——第8章：面向对象设计——题目1

2014-04-23 17:32

题目：请设计一个数据结构来模拟一副牌，你要如何用这副牌玩21点呢？

解法：说实话，扑克牌的花样在于各种花色、顺子、连对、三带一、炸弹等等，如果能设计一个数据结构，让判断这些特征的代码变得很好写，那就能满足题意要求了。我只是勉强实现了几个基本功能，包括抽牌、洗牌、切牌，用的是单向链表。至于要拿这个打斗地主、黑桃五之类的还是算了吧。

代码：

// 8.1 Implement a class to simulate a deck of cards
#include <iostream>
#include <string>
#include <unordered_set>
using namespace std;

struct Poker {
    int index;
    Poker(int _index = 0): index(_index) {};
    
    friend ostream& operator << (ostream &, const Poker &);
};

ostream& operator << (ostream &cout, const Poker &p)
{
    cout << '[';
    if (p.index < 0 || p.index > 53) {
        cout << "ERROR";
    } else if (p.index == 52) {
        cout << "BLACK JOKER";
    } else if (p.index == 53) {
        cout << "RED JOKER";
    } else {
        switch(p.index / 13) {
        case 0:
            cout << "SPADE ";
            break;
        case 1:
            cout << "HEART ";
            break;
        case 2:
            cout << "CLUB ";
            break;
        case 3:
            cout << "DIAMOND ";
            break;
        }
        switch(p.index % 13) {
        case 0:
            cout << 'A';
            break;
        case 1:
        case 2:
        case 3:
        case 4:
        case 5:
        case 6:
        case 7:
        case 8:
            cout << char('1' + p.index % 13);
            break;
        case 9:
            cout << "10";
            break;
        case 10:
            cout << 'J';
            break;
        case 11:
            cout << 'Q';
            break;
        case 12:
            cout << 'K';
            break;
        }
    }
    cout << ']';
    
    return cout;
}

struct PokerListNode {
    Poker p;
    PokerListNode *next;
    PokerListNode(int _index): p(_index), next(nullptr) {};
};

class DeckOfPoker {
public:
    DeckOfPoker() {
        int i;
        
        head = tail = nullptr;
        for (i = 0; i < 54; ++i) {
            if (head == nullptr) {
                head = tail = new PokerListNode(i);
            } else {
                tail->next = new PokerListNode(i);
                tail = tail->next;
            }
            dict.insert(i);
        }
    }
    
    friend ostream& operator << (ostream &, const DeckOfPoker &);
    
    Poker peekCard() {
        if (head == nullptr) {
            return Poker(-1);
        } else {
            return head->p;
        }
    }
    
    Poker getCard() {
        if (head == nullptr) {
            return Poker(-1);
        } else {
            Poker p = head->p;
            PokerListNode *ptr = head;
            head = head->next;
            delete ptr;
            if (head == nullptr) {
                tail = nullptr;
            }
            dict.erase(p.index);
            
            return p;
        }
    }
    
    void insertCard(int index) {
        if (index < 0 || index > 53) {
            return;
        }
        if (dict.find(index) != dict.end()) {
            return;
        }
        
        PokerListNode *ptr = new PokerListNode(index);
        if (head == nullptr) {
            head = tail = ptr;
        } else {
            ptr->next = head;
            head = ptr;
        }
        dict.insert(index);
    }
    
    bool empty() {
        return head == nullptr;
    }
    
    void cutCards() {
        if (head == tail) {
            return;
        }
        
        PokerListNode *p1, *p2;
        p1 = p2 = head;
        while (p2->next != nullptr && p2->next->next != nullptr) {
            p1 = p1->next;
            p2 = p2->next->next;
        }
        PokerListNode *head2 = p1->next;
        p1->next = nullptr;
        
        PokerListNode *new_head, *new_tail;
        
        new_head = new_tail = nullptr;
        p1 = head;
        p2 = head2;
        while (p1 != nullptr && p2 != nullptr) {
            if (new_tail == nullptr) {
                new_head = new_tail = p1;
            } else {
                new_tail->next = p1;
                new_tail = new_tail->next;
            }
            p1 = p1->next;
            new_tail->next = nullptr;
            
            new_tail->next = p2;
            new_tail = new_tail->next;
            p2 = p2->next;
            new_tail->next = nullptr;
        }
        while (p1 != nullptr) {
            new_tail->next = p1;
            new_tail = new_tail->next;
            p1 = p1->next;
            new_tail->next = nullptr;
        }
        while (p2 != nullptr) {
            new_tail->next = p2;
            new_tail = new_tail->next;
            p2 = p2->next;
            new_tail->next = nullptr;
        }
        
        head = new_head;
        tail = new_tail;
    }
    
    void shuffleCards() {
        if (head == tail) {
            // no card or one card only
            return;
        }
        
        PokerListNode *p1, *p2;
        
        p1 = p2 = head;
        while (p2->next != nullptr && p2->next->next != nullptr) {
            p1 = p1->next;
            p2 = p2->next->next;
        }
        tail->next = head;
        head = p1->next;
        p1->next = nullptr;
        tail = p1;
    }
    
    ~DeckOfPoker() {
        PokerListNode *ptr;
        
        while (head != nullptr) {
            ptr = head;
            head = head->next;
            delete ptr;
        }
        tail = head;
        dict.clear();
    }
private:
    PokerListNode *head;
    PokerListNode *tail;
    unordered_set<int> dict;
};

ostream& operator << (ostream& cout, const DeckOfPoker &deck)
{
    cout << '{' << endl;
    if (deck.head == nullptr) {
        cout << "EMPTY" << endl;
    } else {
        PokerListNode *ptr = deck.head;
        
        while (ptr != nullptr) {
            cout << ptr->p << endl;
            ptr = ptr->next;
        }
    }
    cout << '}' << endl;

    return cout;
}

int main()
{
    DeckOfPoker *deck = new DeckOfPoker();
    string s;
    int index;
    
    while (cin >> s) {
        if (s == "insert") {
            cin >> index;
            deck->insertCard(index);
        } else if (s == "peek") {
            cout << deck->peekCard() << endl;
        } else if (s == "get") {
            cout << deck->getCard() << endl;
        } else if (s == "shuffle") {
            deck->shuffleCards();
        } else if (s == "cut"){
            deck->cutCards();
        } else if (s == "print"){
            cout << *deck << endl;
        }
    }
    delete deck;
    
    return 0;
}