c++学习第十二天

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一、string模拟实现

   1.构造和析构

#define _CRT_SECURE_NO_WARNINGS 
#include<iostream>
using namespace std;
#include<string>

namespace bit
{
	class string
	{
	public:
		string()
			:_str(new char[1]{'\0'})
			,_size(0)
			,_capacity(0)
		{}
		string(const char* str = "")
			:_size(strlen(str))
			, _capacity(_size)
		{
			_str = new char[_capacity + 1];
			strcpy(_str, str);
		}
		const char* c_str() const
		{
			return _str;
		}
	private:
		char* _str;
		size_t _size;
		size_t _capacity;
	};
}

int main()
{
	string s1("hello world");
	cout << s1.c_str() << endl;

	string s2;
	cout << s2.c_str() << endl;

	return 0;
}

  2.遍历

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

namespace bit
{
	class string
	{
	public:
		string(const char* str = "")
			:_size(strlen(str))
			, _capacity(_size)
		{
			_str = new char[_capacity + 1];
			strcpy(_str, str);
		}
		char& operator[](size_t pos)
		{
			assert(pos<_size);
			return _str[pos];
		}
		size_t c_size() const
		{
			return _size;
		}
		size_t c_capacity() const
		{
			return _capacity;
		}
		const char* c_str() const
		{
			return _str;
		}
	private:
		char* _str;
		size_t _size;
		size_t _capacity;
	};
}
int main()
{
	string s1("hello world");

	for (size_t i = 0; i < s1.size(); i++)
		cout << s1[i] << " ";

	return 0;
}

3.迭代器

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

namespace bit
{
	class string
	{
	public:
		typedef char* iterator;
		iterator begin()
		{
			return _str;
		}
		iterator end()
		{
			return _str+_size;
		}
		string(const char* str = "")
			:_size(strlen(str))
			, _capacity(_size)
		{
			_str = new char[_capacity + 1];
			strcpy(_str, str);
		}
		char& operator[](size_t pos)
		{
			assert(pos<_size);
			return _str[pos];
		}
		size_t c_size() const
		{
			return _size;
		}
		size_t c_capacity() const
		{
			return _capacity;
		}
		const char* c_str() const
		{
			return _str;
		}
	private:
		char* _str;
		size_t _size;
		size_t _capacity;
	};
}

int main()
{
	string s1("hello world");

	string::iterator it = s1.begin();
	while (it != s1.end())
	{
		cout << *it << " ";
		++it;
	}
	cout << endl;
	for(auto ch:s1)
		cout << ch << " ";

	return 0;
}

4.push_back 、 append 、reserve

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

namespace bit
{
	class string
	{
	public:
		string(const char* str = "")
			:_size(strlen(str))
			, _capacity(_size)
		{
			_str = new char[_capacity + 1];
			strcpy(_str, str);
		}
		void reserve(size_t n)
		{
			if (n > _capacity)
			{
				char* tmp = new char[n + 1];
				strcpy(tmp, _str);
				delete[]  _str;
				_str = tmp;
				_capacity = n;
			}
		}
		void push_back(char ch)
		{
			if (_size == _capacity)
			{
				reserve(_capacity == 0 ? 4 :_capacity * 2);
			}
			_str[_size] = ch;
			_size++;
			_str[_size] = '\0';
		}
		void append(const char* str)
		{
			size_t len = strlen(str);
			if (len + _size > _capacity)
			{
				reserve(len + _size);
			}
			strcpy(_str + _size, str);
			_size += len;
		}
		size_t c_size() const
		{
			return _size;
		}
		size_t c_capacity() const
		{
			return _capacity;
		}
		const char* c_str() const
		{
			return _str;
		}
	private:
		char* _str;
		size_t _size;
		size_t _capacity;
	};
}

int main()
{
	string s1("hello world");
	cout << s1.c_str() << endl;

	s1.push_back('g');
	s1.append("!");
	cout << s1.c_str() << endl;

	return 0;
}

5.+=

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

namespace bit
{
	class string
	{
	public:
		string(const char* str = "")
			:_size(strlen(str))
			, _capacity(_size)
		{
			_str = new char[_capacity + 1];
			strcpy(_str, str);
		}
		void reserve(size_t n)
		{
			if (n > _capacity)
			{
				char* tmp = new char[n + 1];
				strcpy(tmp, _str);
				delete[]  _str;
				_str = tmp;
				_capacity = n;
			}
		}
		void push_back(char ch)
		{
			if (_size == _capacity)
			{
				reserve(_capacity == 0 ? 4 :_capacity * 2);
			}
			_str[_size] = ch;
			_size++;
			_str[_size] = '\0';
		}
		void append(const char* str)
		{
			size_t len = strlen(str);
			if (len + _size > _capacity)
			{
				reserve(len + _size);
			}
			strcpy(_str + _size, str);
			_size += len;
		}
		string& operator+=(char ch)
		{
			push_back(ch);
			return *this;
		}
		string& operator+=(const char* str)
		{
			append(str);
			return *this;
		}
		size_t c_size() const
		{
			return _size;
		}
		size_t c_capacity() const
		{
			return _capacity;
		}
		const char* c_str() const
		{
			return _str;
		}
	private:
		char* _str;
		size_t _size;
		size_t _capacity;
	};
}

int main()
{
	string s1("hello world");
	cout << s1.c_str() << endl;

	s1 += '*';
	s1 += "########";
	cout << s1.c_str() << endl;

	return 0;
}

6.比较运算符

		bool operator<(const string& s) const
		{
			return strcmp(_str, s._str) < 0;
		}
		bool operator==(const string& s) const
		{
			return strcmp(_str, s._str) == 0;
		}
		bool operator<=(const string& s) const
		{
			return *this < s || *this == s;
		}
		bool operator>(const string& s) const
		{
			return !(*this <= s);
		}
		bool operator>=(const string& s) const
		{
			return !(*this < s);
		}
		bool operator!=(const string& s) const
		{
			return !(*this == s);
		}

总结

        以上就是今天要讲的内容，本文仅仅简单介绍了c++基础知识。