【数据结构】string（C++模拟实现）

熙曦Sakura2024-10-12 21:34

string构造

cpp 复制代码 
string::string(const char* str)
	:_size(strlen(str))
{
	_str = new char[_size + 1];
	_capacity = _size;
	strcpy(_str, str);
}

// s2(s1)
string::string(const string& s)
{
	_str = new char[s._capacity + 1];
	strcpy(_str, s._str);
	_size = s._size;
	_capacity = s._capacity;
}

// s1 = s3
// s1 = s1
string& string::operator=(const string& s)
{
	if (this != &s)
	{
		char* tmp = new char[s._capacity + 1];
		strcpy(tmp, s._str);
		delete[] _str;
		_str = tmp;
		_size = s._size;
		_capacity = s._capacity;
	}

	return *this;
}

string::~string()
{
	delete[] _str;
	_str = nullptr;
	_size = _capacity = 0;
}

string容量操作

cpp 复制代码 
const char* string::c_str() const
{
	return _str;
}

size_t string::size() const
{
	return _size;
}

void string::reserve(size_t n)
{
	if (n > _capacity)
	{
		char* tmp = new char[n + 1];
		strcpy(tmp, _str);
		delete[] _str;

		_str = tmp;
		_capacity = n;
	}
}

string类对象的访问和遍历操作

cpp 复制代码 
char& string::operator[](size_t pos)
{
	assert(pos < _size);
	return _str[pos];
}

const char& string::operator[](size_t pos) const
{
	assert(pos < _size);
	return _str[pos];
}
cpp 复制代码 
const size_t string::npos = -1;

string::iterator string::begin()
{
	return _str;
}

string::iterator string::end()
{
	return _str + _size;
}

string::const_iterator string::begin() const
{
	return _str;
}

string::const_iterator string::end() const
{
	return _str + _size;
}

size_t string::find(char ch, size_t pos)
{
	for (size_t i = pos; i < _size; i++)
	{
		if (_str[i] == ch)
		{
			return i;
		}
	}

	return npos;
}

size_t string::find(const char* sub, size_t pos)
{
	char* p = strstr(_str + pos, sub);
	return  p - _str;
}

string类对象的修改操作

cpp 复制代码 
void string::push_back(char ch)
{
	/*if (_size == _capacity)
	{
		size_t newcapacity = _capacity == 0 ? 4 : _capacity * 2;
		reserve(newcapacity);
	}

	_str[_size] = ch;
	_str[_size + 1] = '\0';
	++_size;*/

	insert(_size, ch);
}

// "hello"  "xxxxxxxxxxxxx"
void string::append(const char* str)
{
	/*size_t len = strlen(str);
	if (_size + len > _capacity)
	{
		reserve(_size + len);
	}

	strcpy(_str+_size, str);
	_size += len;*/

	insert(_size, str);
}

string& string::operator+=(char ch)
{
	push_back(ch);

	return *this;
}

string& string::operator+=(const char* str)
{
	append(str);

	return *this;
}

void string::insert(size_t pos, char ch)
{
	assert(pos <= _size);

	if (_size == _capacity)
	{
		size_t newcapacity = _capacity == 0 ? 4 : _capacity * 2;
		reserve(newcapacity);
	}

	/*int end = _size;
	while (end >= (int)pos)
	{
		_str[end + 1] = _str[end];
		--end;
	}*/

	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);
	}

	/*int end = _size;
	while (end >= (int)pos)
	{
		_str[end + len] = _str[end];
		--end;
	}*/

	size_t end = _size + len;
	while (end > pos + len - 1)
	{
		_str[end] = _str[end - len];
		--end;
	}

	memcpy(_str + pos, str, len);
	_size += len;
}

// 17:10
void string::erase(size_t pos, size_t len)
{
	assert(pos < _size);

	// len大于前面字符个数时，有多少删多少
	if (len >= _size - pos)
	{
		_str[pos] = '\0';
		_size = pos;
	}
	else
	{
		strcpy(_str + pos, _str + pos + len);
		_size -= len;
	}
}
// s1.swap(s3)
void string::swap(string& s)
{
	std::swap(_str, s._str);
	std::swap(_size, s._size);
	std::swap(_capacity, s._capacity);
}

string string::substr(size_t pos, size_t len)
{
	// len大于后面剩余字符，有多少取多少
	if (len > _size - pos)
	{
		string sub(_str + pos);
		return sub;
	}
	else
	{
		string sub;
		sub.reserve(len);
		for (size_t i = 0; i < len; i++)
		{
			sub += _str[pos + i];
		}

		return sub;
	}
}

其他函数

cpp 复制代码 
	bool string::operator<(const string& s) const
	{
		return strcmp(_str, s._str) < 0;
	}

	bool string::operator>(const string& s) const
	{
		return !(*this <= s);
	}

	bool string::operator<=(const string& s) const
	{
		return *this < s || *this == s;
	}

	bool string::operator>=(const string& s) const
	{
		return !(*this < s);
	}

	bool string::operator==(const string& s) const
	{
		return strcmp(_str, s._str) == 0;
	}

	bool string::operator!=(const string& s) const
	{
		return !(*this == s);
	}
cpp 复制代码 
void string::clear()
{
	_str[0] = '\0';
	_size = 0;
}

istream& operator>> (istream& is, string& str)
{
	str.clear();
	char ch = is.get();
	while (ch != ' ' && ch != '\n')
	{
		str += ch;
		ch = is.get();
	}

	return is;
}

ostream& operator<< (ostream& os, const string& str)
{
	for (size_t i = 0; i < str.size(); i++)
	{
		os << str[i];
	}

	return os;
}

总结

string.h

cpp 复制代码 
#pragma once

#include<iostream>
#include<assert.h>
using namespace std;

namespace bit
{
	class string
	{
	public:
		typedef char* iterator;
		typedef const char* const_iterator;

		iterator begin();
		iterator end();

		const_iterator begin() const;
		const_iterator end() const;

		//string();
		string(const char* str = "");
		string(const string& s);
		string& operator=(const string& s);
		~string();

		const char* c_str() const;

		size_t size() const;
		char& operator[](size_t pos);
		const char& operator[](size_t pos) const;

		void reserve(size_t n);

		void push_back(char ch);
		void append(const char* str);

		string& operator+=(char ch);
		string& operator+=(const char* str);

		void insert(size_t pos, char ch);
		void insert(size_t pos, const char* str);
		void erase(size_t pos = 0, size_t len = npos);

		size_t find(char ch, size_t pos = 0);
		size_t find(const char* str, size_t pos = 0);

		void swap(string& s);
		string substr(size_t pos = 0, size_t len = npos);

		bool operator<(const string& s) const;
		bool operator>(const string& s) const;
		bool operator<=(const string& s) const;
		bool operator>=(const string& s) const;
		bool operator==(const string& s) const;
		bool operator!=(const string& s) const;
		void clear();
	private:
		// char _buff[16];
		char* _str;

		size_t _size;
		size_t _capacity;

		//  
		//const static size_t npos = -1;

		// ?
		//const static double N = 2.2;

		const static size_t npos;
	};

	istream& operator>> (istream& is, string& str);
	ostream& operator<< (ostream& os, const string& str);
}

string.cpp

cpp 复制代码 
	//string::string()
	//{
	//	_str = new char[1]{'\0'};
	//	_size = 0;
	//	_capacity = 0;
	//}

	string::iterator string::begin()
	{
		return _str;
	}

	string::iterator string::end()
	{
		return _str + _size;
	}

	string::const_iterator string::begin() const
	{
		return _str;
	}

	string::const_iterator string::end() const
	{
		return _str + _size;
	}


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

	// s2(s1)
	string::string(const string& s)
	{
		_str = new char[s._capacity + 1];
		strcpy(_str, s._str);
		_size = s._size;
		_capacity = s._capacity;
	}

	// s1 = s3
	// s1 = s1
	string& string::operator=(const string& s)
	{
		if (this != &s)
		{
			char* tmp = new char[s._capacity + 1];
			strcpy(tmp, s._str);
			delete[] _str;
			_str = tmp;
			_size = s._size;
			_capacity = s._capacity;
		}

		return *this;
	}

	string::~string()
	{
		delete[] _str;
		_str = nullptr;
		_size = _capacity = 0;
	}

	const char* string::c_str() const
	{
		return _str;
	}

	size_t string::size() const
	{
		return _size;
	}

	char& string::operator[](size_t pos)
	{
		assert(pos < _size);
		return _str[pos];
	}

	const char& string::operator[](size_t pos) const
	{
		assert(pos < _size);
		return _str[pos];
	}

	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)
		{
			size_t newcapacity = _capacity == 0 ? 4 : _capacity * 2;
			reserve(newcapacity);
		}

		_str[_size] = ch;
		_str[_size + 1] = '\0';
		++_size;*/

		insert(_size, ch);
	}

	// "hello"  "xxxxxxxxxxxxx"
	void string::append(const char* str)
	{
		/*size_t len = strlen(str);
		if (_size + len > _capacity)
		{
			reserve(_size + len);
		}

		strcpy(_str+_size, str);
		_size += len;*/

		insert(_size, str);
	}

	string& string::operator+=(char ch)
	{
		push_back(ch);

		return *this;
	}

	string& string::operator+=(const char* str)
	{
		append(str);

		return *this;
	}

	void string::insert(size_t pos, char ch)
	{
		assert(pos <= _size);

		if (_size == _capacity)
		{
			size_t newcapacity = _capacity == 0 ? 4 : _capacity * 2;
			reserve(newcapacity);
		}

		/*int end = _size;
		while (end >= (int)pos)
		{
			_str[end + 1] = _str[end];
			--end;
		}*/

		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);
		}

		/*int end = _size;
		while (end >= (int)pos)
		{
			_str[end + len] = _str[end];
			--end;
		}*/

		size_t end = _size + len;
		while (end > pos + len - 1)
		{
			_str[end] = _str[end - len];
			--end;
		}

		memcpy(_str + pos, str, len);
		_size += len;
	}

	// 17:10
	void string::erase(size_t pos, size_t len)
	{
		assert(pos < _size);

		// len大于前面字符个数时，有多少删多少
		if (len >= _size - pos)
		{
			_str[pos] = '\0';
			_size = pos;
		}
		else
		{
			strcpy(_str + pos, _str + pos + len);
			_size -= len;
		}
	}

	size_t string::find(char ch, size_t pos)
	{
		for (size_t i = pos; i < _size; i++)
		{
			if (_str[i] == ch)
			{
				return i;
			}
		}

		return npos;
	}

	size_t string::find(const char* sub, size_t pos)
	{
		char* p = strstr(_str + pos, sub);
		return  p - _str;
	}

	// s1.swap(s3)
	void string::swap(string& s)
	{
		std::swap(_str, s._str);
		std::swap(_size, s._size);
		std::swap(_capacity, s._capacity);
	}

	string string::substr(size_t pos, size_t len)
	{
		// len大于后面剩余字符，有多少取多少
		if (len > _size - pos)
		{
			string sub(_str + pos);
			return sub;
		}
		else
		{
			string sub;
			sub.reserve(len);
			for (size_t i = 0; i < len; i++)
			{
				sub += _str[pos + i];
			}

			return sub;
		}
	}

	bool string::operator<(const string& s) const
	{
		return strcmp(_str, s._str) < 0;
	}

	bool string::operator>(const string& s) const
	{
		return !(*this <= s);
	}

	bool string::operator<=(const string& s) const
	{
		return *this < s || *this == s;
	}

	bool string::operator>=(const string& s) const
	{
		return !(*this < s);
	}

	bool string::operator==(const string& s) const
	{
		return strcmp(_str, s._str) == 0;
	}

	bool string::operator!=(const string& s) const
	{
		return !(*this == s);
	}

	void string::clear()
	{
		_str[0] = '\0';
		_size = 0;
	}

	istream& operator>> (istream& is, string& str)
	{
		str.clear();
		char ch = is.get();
		while (ch != ' ' && ch != '\n')
		{
			str += ch;
			ch = is.get();
		}

		return is;
	}

	ostream& operator<< (ostream& os, const string& str)
	{
		for (size_t i = 0; i < str.size(); i++)
		{
			os << str[i];
		}

		return os;
	}
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