C++類與對象三：String類與循環隊列的實現

一、string類簡單實現

String類簡單實現：

class String
{
public:
	String(const char *str = nullptr)//構造函數
	{
		if (str != nullptr)
		{
			m_data = new char[strlen(str) + 1];
			strcpy(m_data, str);
		}
		else
		{
			m_data = new char[1];//保證String對象一定是一個有效對象
			*m_data = '\0';
		}
	}
	String(const String &other)//拷貝構造函數
	{
		//m_data = other.m_data;默認構造
		m_data = new char[strlen(other.m_data) + 1];
		strcpy(m_data, other.m_data);
	}
	~String(void)//析構函數
	{
		delete[]m_data;
		m_data = nullptr;
	}
	//String&是爲了支持連續的operator=賦值操作
	String& operator= (const String &other)//賦值運算符重載函數
	{
		if (this == &other)
		{
			return *this;
		}

		delete[]m_data;
		m_data = new char[strlen(other.m_data) + 1];
		strcpy(m_data, other.m_data);
		return *this;
	}
private:
	char *m_data;//用於保存字符串
};

int main()
{
	//調用默認構造
	String str1;
	String str2("hello");
	String str3 = "world";

	//調用拷貝構造函數
	String str4 = str3;
	String str5(str3);

	//調用賦值運算符重載函數
	str3 = str1 = str2;
	//賦值從右往左賦
	//str1 = str2;
	//str1.operator=(str2);  =>返回值類型若用void則不行
	//str3 = void;//應該用str1賦給str3 str3 = str1;
	//因此返回值爲當前類型引用是爲支持連續賦值
	return 0;
}

二、循環隊列實現

循環隊列簡單實現：

class Queue
{
public:
	Queue(int size = 5)//構造
	{
		_pQue = new int[size];
		_front = _rear = 0;
		_size = size;
	}
	//Queue(const Queue&) = delete;刪除拷貝構造
	//Queue& operator= (const Queue&) = delete;刪除賦值運算符重載
	Queue(const Queue &src)//拷貝構造
	{
		_size = src._size;
		_front = src._front;
		_rear = src._rear;
		_pQue = new int[_size];
		for (int i=_front; i!=_rear; i=(i+1)%_size)
		{
			_pQue[i] = src._pQue[i];
		}
	}
	Queue& operator= (const Queue &src)//賦值運算符重載
	{
		if (this == &src)
		{
			return *this;
		}
		delete[]_pQue;
		_size = src._size;
		_front = src._front;
		_rear =  src._rear;
		_pQue = new int[_size];
		for (int i=_front; i!=_rear; i=(i+1)%_size)
		{
			_pQue[i] = src._pQue[i];
		}
		return *this;
	}
	~Queue()//析構
	{
		delete[]_pQue;
		_pQue = nullptr;
	}
	void push(int val)//隊尾入隊
	{
		if (full())
		{
			resize();
		}
		_pQue[_rear] = val;
		_rear = (_rear + 1) % _size;//循環隊列
	}
	void pop()//出隊
	{
		if (empty()) return;
		_front = (_front + 1) % _size;//循環隊列
	}
	int front()//獲取隊頭元素
	{
		return _pQue[_front];
	}
	bool full()
	{
		return (_rear+1) % _size == _front;
	}
	bool empty()
	{
		return _front == _rear;
	}
	void resize()
	{
		int *ptmp = new int[2 * _size];
		//擴容後需從fornt遍歷到rear,元素需要從新內存的第0號位元素開始放
		int index = 0;
		for (int i=_front; i!=_rear; i=(i+1)%_size)
		{
			ptmp[index++] = _pQue[i];
		}
		delete[]_pQue;
		_pQue = ptmp;
		_front = 0;
		_rear = index;//元素個數
		_size *= 2;
	}
private:
	int *_pQue;//申請隊列的數組空間
	int _front;//隊頭
	int _rear;//隊尾
	int _size;//隊列擴容的總大小
};

int main()
{
	Queue queue;
	for (int i=0; i<20; ++i)
	{
		queue.push(rand() % 100);
	}

	while (!queue.empty())
	{
		cout << queue.front() << " ";
		queue.pop();
	}
	cout << endl;

	Queue queue1 = queue;
	queue1 = queue;

	return 0;
}

測試一下：測試成功