【深入探索 C++ STL 容器 string】——字符串世界里的神奇魔法棒

//空字符串
string s;

string s("helloworld");

//n个字符char构造
string s(10, 'a');

string s1("helloworld");
//拷贝构造
string s2(s1);

	string s("helloworld");
	cout << s.size() << endl;

	string s("hello");
	cout << s.length() << endl;

	//有效字符个数size为 10，容量capacity为15
	string s("helloworld");
	cout << s.capacity() << endl;

	//有效字符个数size为 10，容量capacity为15
	string s("helloworld");
	cout << s.capacity() << endl;

string s1("helloworld");
cout << s1.size() << endl;
cout << s1.capacity() << endl;
s1.clear();
//清空后为空字符
cout << s1.size() << endl;
cout << s1.capacity() << endl;

string s("hello");
//观察当前容量
cout << s.capacity() << endl;
//如果n小于当前容量，则不会更改容量
s.reserve(10);
cout << s.capacity() << endl;

string s("hello");
//观察当前容量
cout << "string的初始容量："<<s.capacity() << endl;
//如果n大于当前容量，则会更改容量为n，或者更大
s.reserve(20);
cout <<"reserve更改后的容量："<< s.capacity() << endl;

string s("hello");
cout <<"s初始的有效字符个数："<< s.size() << endl;
s.resize(10);
cout << "resize后s的有效字符个数：" << s.size() << endl;

void Test()
{
	string s("hello");
	cout <<"s初始的有效字符个数："<< s.size() << endl;
	s.resize(10,'a');
	cout << "resize后s的有效字符个数：" << s.size() << endl;
}

string s("hello");
cout <<"s初始的有效字符个数："<< s.size() << endl;
cout << "s初始的容量大小：" << s.capacity() << endl;
s.resize(20,'a');
cout << "resize后s的有效字符个数：" << s.size() << endl;
cout << "resize后s的容量：" << s.capacity() << endl;

string s("helloworld");
for (size_t i = 0; i < s.size(); ++i)
{
	cout << s[i] << " ";
}
cout << endl;

string s("helloworld");
for (size_t i = 0; i < s.size(); ++i)
{
	cout << s[i] << " ";
	s[i]+=1;
}
cout << endl;
cout << s << endl;

void Test()
{
	string s("A character sequence");
	auto it = s.begin();
	while (it != s.end())
	{
		cout << *it << " ";
    //修改该位置的字符
		*it += 1;
    //迭代器往后遍历
		++it;
	}
	cout << endl;
	cout <<s<< endl;
}

string s("A character sequence");
auto it = s.rbegin();
while (it != s.rend())
{
	cout << *it << " ";
	*it += 1;
	//反向迭代器也是++
	++it;
}
cout << endl;
cout << s << endl;

string s("hello _zwy!");
for (auto ch : s)
{
	cout << ch << " ";
	ch += 1;
}
cout << endl;

string s("helloworld");
s.push_back('a');
cout << s << endl;
s.push_back('b');
cout << s << endl;
s.push_back('!');
cout << s << endl;

string s("hello");
//追加一个 char* 字符串
s.append("world");
cout << s << endl;

//追加一个string对象
string s1("!world");	
s.append(s1);
cout << s << endl;

//追加n个字符char
s.append(3, '!');
cout << s << endl;

//追加char*字符串的 前n个字符，超出字符串长度，可能会抛异常
s.append("append", 7);
cout << s << endl;

string s1("hello");
string s2("world");
//+=string 对象
s1 += s2;
//+=字符c
s1 += '!';
//+= char* 字符串
s1 += "operator+=";
cout << s1 << endl;

string s("helloworld!");
//字串串的地址会打印出整个字符串
cout << s.c_str() << endl;
//强转为void* 打印地址
cout << (void*)s.c_str() << endl;

string s1("helloworld!");
string s2("hello");
//从默认位置在s1中向后查找string对象
size_t ret1 = s1.find(s2);
cout << "s1在s1中出现的位置:" << ret1 << endl;

//从s1中下标为5向后查找字符 'o'
size_t ret2 = s1.find('o', 5);
cout <<"字符'o'在s1中的位置:" <<ret2 << endl;

//从s1中下标为1向后查找char* 字符串
size_t ret3 = s1.find("world", 1);
cout << "字符串world在s1中的位置：" << ret3 << endl;

//从s1中下标为3向后查找char* 字符串的前n个字符
size_t ret4 = s1.find("loworld!good", 3, 5);
cout << "字符串loworld!good的前5个字符在s1的位置："<< ret4 << endl;

string s("hello world!!");
//从下标为5的位置往前查找字符串"hella"
size_t ret1 = s.rfind("hella",5);
cout << "字符串hella在s中的位置："<<ret1 << endl;

//从下标为5的位置往前查找字符串"hella"的前四个字符
size_t ret2 = s.rfind("hella", 5,4);
cout << "字符串hella的前四个字符在s中的位置：" << ret2 << endl;

string s1("llo wor");
//从默认位置往前查找s1
size_t ret3 = s.rfind(s1);
cout << "string对象s1在s中的位置：" << ret3 << endl;

//从下标为9的位置往前查找字串'r'
size_t ret4=s.rfind('r', 9);
cout << "字符r在s中的位置：" << ret4 << endl;

string str("We think in generalities, but we live in details.");
//截取str前10个字符
string s1 = str.substr(0, 10);
cout << s1 <<  endl;

//截取str从下标5开始的15个字符
string s2 = str.substr(5, 15);
cout << s2 << endl;

//截取整个字符串
string s3 = str.substr();
cout << s3 << endl;

//截取长度超出字符串长度，会截取整个字符串
string s4 = str.substr(3,100);
cout << s4 << endl;

//如果截取位置超过当前字符串长度 会抛出out of range异常
//string s4 = str.substr(80,20);
//cout << s4 << endl;

union _Bxty
{ // storage for small buffer or pointer to larger one
value_type _Buf[_BUF_SIZE];
pointer _Ptr;
char _Alias[_BUF_SIZE]; // to permit aliasing
} _Bx;

struct _Rep_base
{
size_type _M_length;
size_type _M_capacity;
_Atomic_word _M_refcount;
}

// 为了和标准库区分，此处使用String
class String
{
public:

	//以下为错误的string构造函数
	/*String()
	:_str(new char[1])
	{
		*_str = '\0';
	}
	String(const char* str = "\0") 
	String(const char* str = nullptr)*/


	String(const char* str = "")
	{
		// 构造String类对象时，如果传递nullptr指针，可以认为程序非法
		if (nullptr == str)
		{
			assert(false);
			return;
		}
		_str = new char[strlen(str) + 1];
		strcpy(_str, str);
	}
	~String()
	{
		if (_str)
		{
			delete[] _str;
			_str = nullptr;
		}
	}
private:
	char* _str;
};
// 测试
void TestString()
{
	String s1("hello world!!!");
	String s2(s1);
}

class String
{
public:
	//构造函数
	String(const char* str = "")
	{
		if (nullptr == str)
		{
			assert(false);
			return;
		}
		_str = new char[strlen(str) + 1];
		strcpy(_str, str);
	}

	//拷贝构造函数
	String(const String& s)
		: _str(new char[strlen(s._str) + 1])
	{
		strcpy(_str, s._str);
	}

	//赋值重载函数
	String& operator=(const String& s)
	{
		if (this != &s)
		{
			char* pStr = new char[strlen(s._str) + 1];
			strcpy(pStr, s._str);
			delete[] _str;
			_str = pStr;
		}
		return *this;
	}

	//析构函数
	~String()
	{
		if (_str)
		{
			delete[] _str;
			_str = nullptr;
		}
	}
private:
	char* _str;
};

class String
{
public:
	String(const char* str = "")
	{
		if (nullptr == str)
		{
			assert(false);
			return;
		}
		_str = new char[strlen(str) + 1];
		strcpy(_str, str);
	}
	String(const String& s)
		: _str(nullptr)
	{
		String strTmp(s._str);
		swap(_str, strTmp._str);
	}

	// 对比下和上面的赋值那个实现比较好？
	//String& operator=(String s)
	//{
	//	swap(_str, s._str);
	//	return *this;
	//}
	
	String& operator=(const String& s)
	{
		if(this != &s)
		{
			String strTmp(s);
			swap(_str, strTmp._str);
		}
		return *this;
	}
	
	~String()
	{
		if (_str)
		{
			delete[] _str;
			_str = nullptr;
		}
	}
	const char* c_str() const
	{
		return _str;
	}
private:
	char* _str;
};

#define _CRT_SECURE_NO_WARNINGS 1

#pragma once
#include<iostream>
#include<assert.h>
using namespace std;
namespace zwy
{
	class String {
	public:
		typedef char* iterator;
		typedef const char* const_iterator;
		/*	String()
				:_str(new char[1] {'\0'})
				, _size(0)
				, _capacity(0)
			{}

			String(char* str)
			{
				_size = strlen(str);
				_capacity = _size;
				_str = new char[_capacity+1];
				strcpy(_str, str);
			}*/

		iterator begin()
		{
			return _str;
		}

		iterator end()
		{
			return _str + _size;
		}

		const_iterator begin() const
		{
			return _str;
		}

		const_iterator end() const
		{
			return _str + _size;
		}
		String(const char* str = "")
		{
			_size = strlen(str);
			_capacity = _size;
			_str = new char[_capacity + 1];
			strcpy(_str, str);
		}
		~String()
		{
			if (_str) 
			{
				delete[] _str;
				_str = nullptr;
				_size = _capacity = 0;
			}
			
		}

		//ͳд
		//s1(s2)
	  /* String(const String& str)
		{
		   _str = new char [str._capacity + 1];
		   strcpy(_str,str._str);
		   _size = str._size;
		   _capacity = str._capacity;
		}*/
	   
	   void Swap(String& str)
	   {
		   std::swap(_str, str._str);
		   std::swap(_size, str._size);
		  std:: swap(_capacity, str._capacity);
	   }

	   //ִд
	   String(const String& str)
	   {
		   String tmp(str._str);
		   Swap(tmp);
	   }


	   //String& operator=(const String& str)
	   //{
		  // if (this != &str)
		  // {
			 //  delete[] _str;

			 //  _str = new char[str._capacity + 1];
			 //  strcpy(_str, str._str);
			 //  _size = str._size;
			 //  _capacity = str._capacity;
		  // }
		  // return *this;
	   //}


	   //s1=s2
	/*   String& operator=(const String& str)
	   {
		   if (this != &str)
		   {
			   String tmp(str._str);
			   Swap(tmp);
		   }
		   return *this;
	   }*/

	   String& operator=( String tmp)
	   {
			   Swap(tmp);
		   return *this;
	   }

		size_t size() const
		{
			return _size;
		}

		size_t capacity() const
		{
			return _capacity;
		}
		const char* c_str() const
		{
			return _str;
		}


		void clear()
		{
			_str[0] = '\0';
			_size = 0;
		}
	
		//bool empty()const;

		void reserve(size_t n);
		void push_back(char ch);
		String& operator+=(char ch);
		String& operator+=(const char* str);
		void append(const char* str);
		void insert(size_t pos, char ch);
		void insert(size_t pos, const char* str);
		void erase(size_t pos, size_t len = npos);
		size_t find(char ch, size_t pos = 0);
		size_t find(const char* str, size_t pos = 0);
		String substr(size_t pos = 0, size_t len = npos);
	private:
		char* _str=nullptr;
		size_t _size = 0;
		size_t _capacity=0;
		static const size_t npos;
	};
	ostream& operator<<(ostream& out, const String& str);
	istream& operator>>(istream& in, String& str);
	bool operator<(const String& s1, const String& s2);
	bool operator<=(const String& s1, const String& s2);
	bool operator>(const String& s1, const String& s2);
	bool operator>=(const String& s1, const String& s2);
	bool operator==(const String& s1, const String& s2);
	bool operator!=(const String& s1, const String& s2);
}

#include"String.h"

namespace zwy {
	const size_t String::npos = -1;
	void String::reserve(size_t n)
	{
		if (n > _capacity)
		{
			char* tmp = new char[n + 1];
			strcpy(tmp, _str);
			delete[] _str;
			_str = tmp;
			_capacity = n;
		}
	}

	void String::push_back(char ch)
	{
		if (_size == _capacity)
		{
			reserve(_capacity == 0 ? 4 : 2 * _capacity);
		}
		_str[_size] = ch;
		++_size;
		_str[_size] = '\0';
	}

	String& String:: operator+=(char ch)
	{
		push_back(ch);
		return *this;
	}


	String& String::operator+=(const char* str)
	{
		append(str);
		return *this;
	}


	void String::append(const char* str)
	{
		size_t len = strlen(str);
		if (_size + len > _capacity)
		{
			reserve(_size + len > 2 * _capacity ? _size + len : 2 * _capacity);
		}
		strcpy(_str + _size, str);
		_size += len;
	}

	void String::insert(size_t pos, char ch)
	{
		assert(pos < _size);
		if (_size == _capacity)
		{
			reserve(_capacity == 0 ? 4 : 2 * _capacity);
		}
		size_t end = _size + 1;
		while (end > pos)
		{
			_str[end] = _str[end - 1];
			--end;
		}
		_str[pos] = ch;
		++_size;
	}


	void String::insert(size_t pos, const char* str)
	{
		assert(pos < _size);
		size_t len = strlen(str);
		if (_size + len > _capacity)
		{
			reserve(_size + len > 2 * _capacity ? _size + len : 2 * _capacity);
		}
		size_t end = _size + len;
		while (end>pos+len-1)
		{
			_str[end] = _str[end-len];
			--end;
	   }
		for (size_t i = 0; i < len; i++)
		{
			_str[pos + i] = str[i];
		}
		_size += len;
	}

	void String::erase(size_t pos, size_t len)

	{
		assert(pos < _size);
		if (len > _size - pos)
		{
			_str[pos] = '\0';
			_size = pos;
		}
		else {
			for (size_t i = pos + len; i <= _size; i++)
			{
				_str[i - len] = _str[i];
			}
			_size -= len;
			}
	}

	size_t String::find(char ch, size_t pos)
	{
		assert(pos < _size);
		for (size_t i = 0; i < _size; i++)
		{
			if (_str[i] == ch)
				return i;
		}
		return npos;
	}
	size_t String::find(const char* str, size_t pos)
	{
		assert(pos < _size);
		const char* ptr = strstr(_str + pos, str);
		if (ptr == nullptr)
		{
			return npos;
		}
		return ptr - _str;
	}

	String String::substr(size_t pos, size_t len)
	{
		assert(pos < _size);
		if (len > _size - pos)
		{
			len = _size - pos;
		}
		String sub;
		sub.reserve(len);
		for (size_t i=0; i < len; i++)

		{
			sub += _str[pos + i];
		}
		return sub;
	}

	bool operator<(const String& s1, const String& s2)
	{
		return strcmp(s1.c_str(), s2.c_str()) < 0;
	}
	bool operator<=(const String& s1, const String& s2)
	{
		return s1 < s2 || s1 == s2;
	}
	bool operator>(const String& s1, const String& s2)
	{
		return !(s1 <= s2);
	}
	bool operator>=(const String& s1, const String& s2)
	{
		return !(s1 < s2);
	}
	bool operator==(const String& s1, const String& s2)
	{
		return strcmp(s1.c_str(), s2.c_str()) == 0;
	}
	bool operator!=(const String& s1, const String& s2)
	{
		return !(s1 == s2);
	}

	ostream& operator<<(ostream& out, const String& str)
	{
		for (auto ch : str)
		{
			out << ch;
		}
		return out;
	}
	istream& operator>>(istream& in, String& str)
	{

		//
		str.clear();
		char ch;
		const int N = 256;
		char buff[N];
		int i = 0;
		ch = in.get();
		while (ch != ' ' && ch != '\n')
		{
			buff[i++] = ch;
			if (i == N - 1)
			{
				str += buff;
				i = 0;
			}
			ch = in.get();
		}
		if (i > 0)
		{
			buff[i] = '\0';
			str += buff;
		}
		return in;
	}
}