《C++游戏编程入门》第4章 标准模板库: Hangman

4.1 标准模板库

Standard Template Library，提供算法、容器和迭代器等。

4.2 vector

动态数组。
优势：

• 根据需要动态增长。
• 和STL算法使用，获得查找排序等功能。

缺点：

• 额外内存开销。
• 增长时可能性能损失。
• 某些游戏控制台系统无法使用向量。

04.heros_inventory2.cpp

#include <iostream>
#include <string>
#include <vector>
using namespace std;int main()
{vector<string> inventory; // 声明// 添加元素inventory.push_back("sword");inventory.push_back("armor");inventory.push_back("shield");cout << "You have " << inventory.size() << " items.\n"; // 向量大小cout << "\nYour items:\n";for (unsigned int i = 0; i < inventory.size(); ++i){cout << inventory[i] << endl; // 向量索引}cout << "\nYou trade your sword for a battle axe.";inventory[0] = "battle axe"; // 向量元素赋值cout << "\nYour items:\n";for (unsigned int i = 0; i < inventory.size(); ++i){cout << inventory[i] << endl;}cout << "\nThe item name '" << inventory[0] << "' has ";cout << inventory[0].size() << " letters in it.\n";cout << "\nYour shield is destroyed in a fierce battle.";inventory.pop_back(); // 移除最后一个元素cout << "\nYour items:\n";for (unsigned int i = 0; i < inventory.size(); ++i){cout << inventory[i] << endl;}cout << "\nYou were robbed of all of your possessions by a thief.";inventory.clear();	   // 移除所有元素if (inventory.empty()) // 判断是否为空{cout << "\nYou have nothing.\n";}else{cout << "\nYou have at least one item.\n";}return 0;
}

4.3 使用迭代器

迭代器标识容器中某个特定元素的值，引用元素。

04.heros_inventory3.cpp

#include <iostream>
#include <string>
#include <vector>
using namespace std;int main()
{vector<string> inventory;inventory.push_back("sword");inventory.push_back("armor");inventory.push_back("shield");vector<string>::iterator myIterator; // 迭代器声明vector<string>::const_iterator iter; // 常量迭代器，不能修改相应元素cout << "Your items:\n";for (iter = inventory.cbegin(); iter != inventory.cend(); ++iter){cout << *iter << endl;}cout << "\nYou trade your sword for a battle axe.";myIterator = inventory.begin();*myIterator = "battle axe";cout << "\nYour items:\n"; // 循环访问向量// 第一个元素，最后一个元素之后，更新for (iter = inventory.begin(); iter != inventory.end(); ++iter){cout << *iter << endl; // 解引用}cout << "\nThe item name '" << *myIterator << "' has ";cout << (*myIterator).size() << " letters in it.\n";cout << "\nThe item name '" << *myIterator << "' has ";cout << myIterator->size() << " letters in it.\n";cout << "\nYou recover a crossbow from a slain enemy.";inventory.insert(inventory.begin(), "crossbow"); // 插入元素cout << "\nYour items:\n";for (iter = inventory.begin(); iter != inventory.end(); ++iter){cout << *iter << endl;}cout << "\nYour armor is destroyed in a fierce battle.";inventory.erase((inventory.begin() + 2)); // 移除元素cout << "\nYour items:\n";for (iter = inventory.begin(); iter != inventory.end(); ++iter){cout << *iter << endl;}return 0;
}

4.4 使用算法

泛型，同样算法用于不同容器类型的元素。

04.high_scores.cpp

#include <iostream>
#include <vector>
#include <algorithm>
#include <ctime>
#include <cstdlib>
using namespace std;int main()
{vector<int>::const_iterator iter;cout << "Creating a list of scores.";vector<int> scores;scores.push_back(1500);scores.push_back(3500);scores.push_back(7500);cout << "\nHigh Scores:\n";for (iter = scores.begin(); iter != scores.end(); ++iter){cout << *iter << endl;}cout << "\nFinding a score.";int score;cout << "\nEnter a score to find: ";cin >> score;iter = find(scores.begin(), scores.end(), score); // 查找if (iter != scores.end()){cout << "Score found.\n";}else{cout << "Score not found.\n";}cout << "\nRandomizing scores.";srand(static_cast<unsigned int>(time(0)));random_shuffle(scores.begin(), scores.end()); // 随机重排cout << "\nHigh Scores:\n";for (iter = scores.begin(); iter != scores.end(); ++iter){cout << *iter << endl;}cout << "\nSorting scores.";sort(scores.begin(), scores.end()); // 排序cout << "\nHigh Scores:\n";for (iter = scores.begin(); iter != scores.end(); ++iter){cout << *iter << endl;}string word = "High Scores";random_shuffle(word.begin(), word.end());for (auto it = word.cbegin(); it != word.cend(); ++it)cout << *it << endl;return 0;
}

4.5 理解向量性能

向量添加新元素超过当前大小时，重新分配内存，可能全部元素重新复制，导致性能损失。
capacity()向量容量，预先多分配空间。
reserve()扩充容量。
push_back()或pop_back()，尾部添加或移除元素效率高。
insert()或erase()，中间添加或移除元素效率底。

4.6 其他STL容器

顺序型容器：依次检索元素值。
关联型容器：基于键值检索元素值。

deque、list、map、multimap、multiset、priority_queue、queue、set、stack、vector

4.7 Hangman简介

04.hangman.cpp

#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <ctime>
#include <cctype>
using namespace std;int main()
{// 常量、变量初始化const int MAX_WRONG = 8; // maximum number of incorrect guesses allowedvector<string> words; // collection of possible words to guesswords.push_back("GUESS");words.push_back("HANGMAN");words.push_back("DIFFICULT");srand(static_cast<unsigned int>(time(0)));random_shuffle(words.begin(), words.end());const string THE_WORD = words[0];   // word to guessint wrong = 0;                      // number of incorrect guessesstring soFar(THE_WORD.size(), '-'); // word guessed so farstring used = "";                   // letters already guessedcout << "Welcome to Hangman.  Good luck!\n";// main loopwhile ((wrong < MAX_WRONG) && (soFar != THE_WORD)){cout << "\n\nYou have " << (MAX_WRONG - wrong);cout << " incorrect guesses left.\n";cout << "\nYou've used the following letters:\n"<< used << endl;cout << "\nSo far, the word is:\n"<< soFar << endl;char guess;cout << "\n\nEnter your guess: ";cin >> guess;guess = toupper(guess); // make uppercase since secret word in uppercasewhile (used.find(guess) != string::npos){cout << "\nYou've already guessed " << guess << endl;cout << "Enter your guess: ";cin >> guess;guess = toupper(guess);}used += guess;if (THE_WORD.find(guess) != string::npos){cout << "That's right! " << guess << " is in the word.\n";// update soFar to include newly guessed letterfor (unsigned int i = 0; i < THE_WORD.length(); ++i){if (THE_WORD[i] == guess){soFar[i] = guess;}}}else{cout << "Sorry, " << guess << " isn't in the word.\n";++wrong;}}// shut downif (wrong == MAX_WRONG)cout << "\nYou've been hanged!";elsecout << "\nYou guessed it!";cout << "\nThe word was " << THE_WORD << endl;return 0;
}