数组，避免拉重复，简单代码，C++

Question

这是一个纸牌游戏，我在两个函数的帮助下从牌组(数组(中抽取2张牌。

阵列中的每个元素代表一张带有黑桃、红心、钻石或梅花符号的牌。

数组\5\4\3\6中的这些数字代表球杆、Dimaond、Heaters、spades(如果你好奇的话(

问题来了

当我抽两次牌时，有时会出现重复。。同一张牌两次。

如何确保同一张牌不能抽两次？如何避免重复？？

这就是代码的样子。

有关阵列的一些信息。。。在数组中，元素的值越高。我缩短了数组。。。为了简单地测试解决方案。。。稍后该阵列将是52个元素。

array<string, 3> cards = { "Ess 5", "Ess 4", "Ess 3" };

//The function.
pair<string, int> draw_card()
{
int random_index = rand() % 52;
string card = cards[random_index];
return { card, random_index };
}
int main()
{
// Seed, random.
srand((unsigned int)time(NULL));

// Calling the function 2 times.
pair<string, int> you_drew = draw_card();
cout << "You drew: " << you_drew.first << endl;
pair<string, int> comp_drew = draw_card();
cout << "Computer drew: " << comp_drew.first << endl;

// Deciding the winner.
int your_score{ 0 };
int the_computers_score{ 0 };
if (you_drew.second > comp_drew.second) {
cout << "You Won!" << endl;
your_score++;
}
else if (you_drew.second < comp_drew.second) {
cout << "You Lost!" << endl;
the_computers_score++;
}
return 0;
}

一切都很好，除了有时我会收到副本。。。我想确保我不能。。。不知怎的，当我画一张牌时，数组中的元素应该无法绘制。。我想避免重复。请帮帮我！

像这样的东西不应该工作吗？不是而是。。不是吗？

pair<string, int> comp_drew = draw_card();
if (you_drew == comp_drew) {
bool run8 = true;
while (run8) {
pair<string, int> comp_drew = draw_card();

if (comp_drew != you_drew) {
cout << "Computer drew: " << comp_drew.first << endl;
run8 = false;
}
}
}

或者另一种解决方案。。也许在调用函数一次之后，我可以从数组中删除返回索引？

Answer 1

您可以将抽到的卡片交换到最后，下次只选择小于51的索引。

int array_len = 52; // global variables are not great, but it's easier here
pair<string, int> draw_card()
{
int random_index = rand() % array_len;
--array_len;
string card = cards[random_index];
std::swap(cards[random_index], cards[array_len]);

return { card, random_index };
}

Answer 2

有很多不同的方法可以做到这一点。

std:：random_shuffle

#include <iostream>
#include <algorithm>
using namespace std;
class CardMachine {
static unsigned constexpr DECK_SIZE = 4;
int cards[DECK_SIZE] = {1,2,3,4};
int lastUsedCardIndex = -1;
public:
int getCard() {
if (lastUsedCardIndex == DECK_SIZE - 1)
shuffle();
return cards[++lastUsedCardIndex];
}

void shuffle() {
random_shuffle(begin(cards), end(cards));
}
};
int main()
{
CardMachine cardMachine = CardMachine();

cout << "unhsuffled - 1,2,3,4 without duplicates:" << endl;
cout << cardMachine.getCard() << endl;
cout << cardMachine.getCard() << endl;
cout << cardMachine.getCard() << endl;
cout << cardMachine.getCard() << endl;

cout << "Shuffled. Random order, and still no duplicates:" << endl;
cardMachine.shuffle(); // or call getCard which can shuffle
cout << cardMachine.getCard() << endl;
cout << cardMachine.getCard() << endl;
cout << cardMachine.getCard() << endl;
cout << cardMachine.getCard() << endl;
return EXIT_SUCCESS;
}

将卡片标记为已取走

#include <iostream>
#include <random>
using namespace std;
class CardMachine {
static unsigned constexpr DECK_SIZE = 4;
inline static int constexpr cards[DECK_SIZE] = {1,2,3,4};
bool cardIsGone[DECK_SIZE] = {false, false, false, false};
public:
int getCard() {
while(true) {
int const RANDOM_INDEX = rand()%DECK_SIZE;
if(!cardIsGone[RANDOM_INDEX]) {
cardIsGone[RANDOM_INDEX] = true;
return cards[RANDOM_INDEX];
}
}
}

void shuffle() {
for(bool &isGone : cardIsGone)
isGone = false;
lastUsedCardIndex = -1;
}
};
int main()
{
CardMachine cardMachine = CardMachine();

cout << "Shuffled - Random order, and still no duplicates:" << endl;
cout << cardMachine.getCard() << endl;
cout << cardMachine.getCard() << endl;
cout << cardMachine.getCard() << endl;
cout << cardMachine.getCard() << endl;

cout << "Shuffled. Random order, and still no duplicates:" << endl;
cardMachine.shuffle(); // Causes infinite loop if you call getCard DECK_SIZE + 1 times
cout << cardMachine.getCard() << endl;
cout << cardMachine.getCard() << endl;
cout << cardMachine.getCard() << endl;
cout << cardMachine.getCard() << endl;
return EXIT_SUCCESS;
}

这不是最有效的解决方案，但对于像52这样的小值，它应该是即时的。

将用过的卡交换到背面并跟踪范围

#include <iostream>
#include <random>
using namespace std;
class CardMachine {
static unsigned constexpr DECK_SIZE = 4;
int cards[DECK_SIZE] = {1,2,3,4};
int lastCardIndexExlusive = DECK_SIZE;
public:
int getCard() {
int const RANDOM_INDEX = rand()%lastCardIndexExlusive;
swap(cards[RANDOM_INDEX],cards[lastCardIndexExlusive - 1]);
return cards[--lastCardIndexExlusive];
}

void shuffle() {
lastCardIndexExlusive = DECK_SIZE;
}
};
int main()
{
CardMachine cardMachine = CardMachine();

cout << "Shuffled - Random order, and still no duplicates:" << endl;
cout << cardMachine.getCard() << endl;
cout << cardMachine.getCard() << endl;
cout << cardMachine.getCard() << endl;
cout << cardMachine.getCard() << endl;

cout << "Shuffled. Random order, and still no duplicates:" << endl;
cardMachine.shuffle(); // Causes exception if getCard DECK_SIZE + 1 times
cout << cardMachine.getCard() << endl;
cout << cardMachine.getCard() << endl;
cout << cardMachine.getCard() << endl;
cout << cardMachine.getCard() << endl;
return EXIT_SUCCESS;
}

记住最后一张卡

#include <iostream>
#include <random>
using namespace std;
class CardMachine {
static unsigned constexpr DECK_SIZE = 4;
int cards[DECK_SIZE] = {1,2,3,4};
int lastCard = -1;
public:
int getCard() {
int const RANDOM_INDEX = rand()%DECK_SIZE;
if (lastCard == RANDOM_INDEX) {
return getCard();
}
lastCard = cards[RANDOM_INDEX];
return lastCard;
}

void shuffle() {
lastCard = -1;
}
};
int main()
{
CardMachine cardMachine = CardMachine();

cout << "Shuffled - Random order, and still no duplicates, but only able to produce 2:" << endl;
cout << cardMachine.getCard() << endl;
cout << cardMachine.getCard() << endl;
cout << "Shuffled. Random order, and still no duplicates:" << endl;
cardMachine.shuffle(); // Causes potential duplicates if getCards 3+ times
cout << cardMachine.getCard() << endl;
cout << cardMachine.getCard() << endl;
return EXIT_SUCCESS;
}

所有这些解决方案都使用类来保持状态，以便在getCard中使用，以确保我们获得正确的行为。