string 模拟与用法

string 用法

string

string 模拟

#pragma once
#include 
#include 
#include 

namespace sjy
{
	class string
	{
	public:
		//迭代器相关
		typedef char* iterator;
		typedef const char* const_iterator;
		iterator begin()
		{
			return _str;
		}
		iterator end()
		{
			return _str + _size;
		}
		const_iterator begin() const
		{
			return _str;
		}
		const_iterator end() const
		{
			return _str + _size;
		}

		//默认成员函数
		string(const char* str = "")
		{
			size_t len = strlen(str);
			_size = len;
			_capacity = len;
			_str = new char[_capacity + 1]{ 0 };
			memcpy(_str, str, sizeof(char) * (_size + 1));
		}
		~string()
		{
			delete[] _str;
			_str = nullptr;
			_size = _capacity = 0;
		}
		string(const string& other)
		{
			_size = other._size;
			_capacity = other._capacity;
			_str = new char[_capacity + 1]{ 0 };
			memcpy(_str, other._str, sizeof(char) * (_size + 1));
		}
		string& operator=(string other)
		{
			swap(other);
			return *this;
		}

		//size, capacity相关
		size_t size() const
		{
			return _size;
		}
		size_t capacity() const
		{
			return _capacity;
		}
		void resize(size_t n, char c = '\0')
		{
			if (n < _size)
			{
				*(_str + n) = '\0';
				_size = n;
			}
			else
			{
				reserve(n);
				for (int i = _size; i < n; i++)
				{
					*(_str + i) = c;
				}
				*(_str + n) = '\0';
				_size = n;
			}
		}
		void reserve(size_t n = 0)
		{
			if (n > _capacity)
			{
				_capacity = n;
				char* tmp = new char[_capacity + 1]{ 0 };
				memcpy(tmp, _str, sizeof(char) * (_size + 1));
				delete[] _str;
				_str = tmp;
			}
		}

		//添加修改相关
		char& operator[](size_t pos)
		{
			assert(pos < _size);
			return *(_str + pos);
		}
		const char& operator[](size_t pos) const
		{
			assert(pos < _size);
			return *(_str + pos);
		}
		void push_back(char c)
		{
			if (_size == _capacity)
			{
				reserve(_capacity == 0 ? 4 : 2 * _capacity);
			}
			*(_str + _size) = c;
			_size++;
			*(_str + _size) = '\0';
		}
		void append(const char* str)
		{
			size_t len = strlen(str);
			if (_size + len > _capacity)
			{
				reserve(_size + len);
			}
			for (int i = 0; i <= len; i++)
			{
				*(_str + _size + i) = *(str + i);
			}
			_size += len;
		}
		string& operator+=(char c)
		{
			push_back(c);
			return *this;
		}
		string& operator+=(const char* str)
		{
			append(str);
			return *this;
		}
		void insert(size_t pos, size_t n, char c)
		{
			assert(pos <= _size);
			if (_size + n > _capacity)
			{
				reserve(_size + n);
			}
			for (int i = _size + n; i >= pos + n && i != npos; i--)
			{
				*(_str + i) = *(_str + i - n);
			}
			for (int i = 0; i < n; i++)
			{
				*(_str + pos + i) = c;
			}
			_size += n;
		}
		void insert(size_t pos, const char* str)
		{
			assert(pos <= _size);
			size_t len = strlen(str);
			if (_size + len > _capacity)
			{
				reserve(_size + len);
			}
			for (int i = _size + len; i >= pos + len && i != npos; i--)
			{
				*(_str + i) = *(_str + i - len);
			}
			for (int i = 0; i < len; i++)
			{
				*(_str + pos + i) = *(str + i);
			}
			_size += len;
		}

		//删除相关
		string& erase(size_t pos = 0, size_t len = npos)
		{
			assert(pos <= _size);
			if (len == npos || pos + len >= _size)
			{
				*(_str + pos) = '\0';
				_size = pos;
			}
			else
			{
				for (int i = pos + len; i <= _size; i++)
				{
					*(_str + i - len) = *(_str + i);
				}
				_size -= len;
			}
			return *this;
		}

		//查找与字符串相关
		size_t find(char c, size_t pos = 0) const
		{
			for (int i = pos; i < _size; i++)
			{
				if (*(_str + i) == c)
				{
					return i;
				}
			}
			return npos;
		}
		size_t find(const char* str, size_t pos = 0) const
		{
			const char* ptr = strstr(_str + pos, str);
			if (ptr == nullptr)
			{
				return npos;
			}
			else
			{
				return ptr - _str;
			}
		}
		string substr(size_t pos = 0, size_t len = npos) const
		{
			assert(pos < _size);
			if (len == npos || pos + len > _size)
			{
				len = _size - pos;
			}
			char* tmp = new char[len + 1]{ 0 };
			for (int i = 0; i < len; i++)
			{
				*(tmp + i) = *(_str + pos + i);
			}
			string str(tmp);
			delete[] tmp;
			return str;
		}

		//其他
		const char* c_str()
		{
			return _str;
		}
		void clear()
		{
			_size = 0;
			*_str = '\0';
		}
		void swap(string& str)
		{
			std::swap(_str, str._str);
			std::swap(_size, str._size);
			std::swap(_capacity, str._capacity);
		}
		bool operator<(const string& str) const
		{
			int size1 = this->_size;
			int size2 = str._size;
			int minsize = size1 < size2 ? size1 : size2;
			for (int i = 0; i < minsize; i++)
			{
				if (*(_str + i) > *(str._str + i))
				{
					return false;
				}
				else if (*(_str + i) < *(str._str + i))
				{
					return true;
				}
			}
			if (size1 == size2 || size1 > size2)
			{
				return false;
			}
			else if (size1 < size2)
			{
				return true;
			}
		}
		bool operator==(const string& str) const
		{
			if (_size == str._size && memcmp(_str, str._str, sizeof(char) * _size) == 0)
			{
				return true;
			}
			return false;
		}
		bool operator>(const string& str) const
		{
			return !((*this) < str || (*this) == str);
		}
		bool operator<=(const string& str) const
		{
			return ((*this) < str || (*this) == str);
		}
		bool operator>=(const string& str) const
		{
			return ((*this) > str || (*this) == str);
		}
	private:
		char* _str;
		size_t _size;
		size_t _capacity;
		static size_t npos;
	};
	size_t string::npos = -1;
	std::istream& operator>>(std::istream& cin, string& str)
	{
		str.clear();
		char c = cin.get();
		while (c == ' ' || c == '\0')
		{
			c = cin.get();
		}
		char buff[128] = { 0 };
		int i = 0;
		while (c != ' ' && c != '\0')
		{
			buff[i++] = c;
			if (i == 127)
			{
				str += buff;
				i = 0;
			}
			c = cin.get();
		}
		if (i != 0)
		{
			*(buff + i) = '\0';
			str += buff;
		}
		return cin;
	}
	std::ostream& operator<<(std::ostream& cout, const string& str)
	{
		for (auto c: str)
		{
			cout << c;
		}
		return cout;
	}
}