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文章目录
-
- :heartbeat:模拟实现string头文件
- 1.:maple_leaf:iterator begin();和iterator end();:maple_leaf:const_iterator begin() const;和const_iterator end() const;
- 2.:maple_leaf:构造函数和拷贝构造函数
- 3.:maple_leaf:析构函数
- 4.:maple_leaf:赋值重载函数
- 5.:maple_leaf:const char* c_str() const;
- 6.:maple_leaf:size_t size() const;
- 7. :maple_leaf:[]运算符重载
- 8.:maple_leaf:void reserve(size_t n);
- 9.:maple_leaf:void push_back(char ch);
- 10.:maple_leaf:void append(const char* str);
- 11.:maple_leaf:+=运算符重载函数
- 12.:maple_leaf:insert的实现
- 13.:maple_leaf:void erase(size_t pos = 0, size_t len = npos);
- 14.:maple_leaf:find函数实现
- 15.:maple_leaf:swap函数的实现
- 16.:maple_leaf:substr的实现
- 17.:maple_leaf:运算符重载
- 18.:maple_leaf:>>重载函数和<<重载函数
🍁💓
💓模拟实现string头文件
#pragma once
#include<iostream>
#include<assert.h>
using namespace std;
namespace My_string
{
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=(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 = nullptr;
size_t _size = 0;
size_t _capacity = 0;
const static size_t npos;
};
istream& operator>> (istream& is, string& str);
ostream& operator<< (ostream& os, const string& str);
}
1.🍁iterator begin();和iterator end();🍁const_iterator begin() const;和const_iterator end() const;
之前说过iterator是个类指针的工具,所以我们在这里用指针的方式模拟:
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;
}
2.🍁构造函数和拷贝构造函数
🍃构造函数
string::string(const char* str)
:_size(strlen(str))
{
_str = new char[_size + 1];
_capacity = _size;
strcpy(_str, str);
}
🍃拷贝构造函数
这里复用构造函数:
string:string(const string& s)
{
string tmp(s._str);
swap(tmp);
}
3.🍁析构函数
string::~string()
{
_size = _capacity = 0;
delete[] _str;
_str = nullptr;
}
4.🍁赋值重载函数
🍃传统写法:
string& string::operator=(const string& s)
{
if(this != &s)
{
char* tmp = new char[s._capacity + 1];
strcpy(tmp,s._str);
delete[] _str;
_size = s._size;
_capacity = s._capacity;
_str = tmp;
}
return *this;
}
🍃现代写法:
这里用传值传参,形成一个实参的临时拷贝,也就是复用了拷贝构造函数:
string& string::operator=(string s)
{
swap(s);// 让别人来干活
return *this;
}
5.🍁const char* c_str() const;
const char* string::c_str() const
{
return _str;
}
6.🍁size_t size() const;
size_t string::size()const
{
return _size;
}
7. 🍁[]运算符重载
🍃char& operator[](size_t pos);
char& string::operator[](size_t pos)
{
assert(pos < _size);
return _str[pos];
}
🍃const char& operator[](size_t pos) const;
const char& string::operator[](size_t pos) const
{
assert(pos < _size);
return _str[pos];
}
8.🍁void reserve(size_t n);
void string::reserve(size_t n)
{
if (_capacity < n)
{
char* tmp = new char[n + 1];
strcpy(tmp,_str);
delete[] _str;
_str = tmp;
_capacity = n;
}
}
9.🍁void push_back(char ch);
🍃在实现insert
之前的写法:
void string::push_back(char ch)
{
if(_size == _capacity)
{
size_t newcapacity = _capacity == 0 ? 4 : 2*_capacity;
reserve(newcapacity);
}
_str[_size] = ch;
_str[_size + 1] = '\0';
++_size;
}
🍃在实现insert
之后的写法:
void string::push_back(char ch)
{
insert(_size,ch);
}
10.🍁void append(const char* str);
🍃在实现insert
之前的写法:
void string::append(const char* str)
{
size_t len - strlen(str);
if(_size + len >= _capacity)
{
size_t newcapacity = _capacity == 0 ? 4 : 2*_capacity;
reserve(newcapacity);
}
strcpy(_str + _size, str);
_size += len;
}
🍃在实现insert
之后的写法:
void string::append(const char* str)
{
insert(_size,str);
}
11.🍁+=运算符重载函数
🍃string& operator+=(char ch);
string& string::operator+=(char ch)
{
push_back(ch);
return *this;
}
🍃string& operator+=(const char* str);
string& string::operator+=(const char str)
{
append(str);
return *this;
}
12.🍁insert的实现
🍃void insert(size_t pos, char ch);
void string::insert(size_t pos, char ch)
{
assert(pos <= _size);
if(_size == _capacity)
{
size_t newcapacity = _capacity == 0 ? 4 : 2*_capacity;
reserve(newcapacity);
}
size_t end = _size + 1;
while(end > pos)
{
_str[end] = _str[end - 1];
--end;
}
_str[pos] = ch;
++_size;
}
🍃void insert(size_t pos, const char* str);
void string::insert(size_t pos, const char* str)
{
assert(pos <= _size);
size_t len = strlen(str);
if(_size + len > _capacity)
{
reserve(_size + len);
}
size_t end = _size + len;
while(end >= pos + len)
{
_str[end] = _str[end - len];
--end;
}
memcpy(_str + pos,str,len);
// 由于strcpy会将后面的字符覆盖,所以这里要用memcpy
_size += len;
}
13.🍁void erase(size_t pos = 0, size_t len = npos);
const size_t string::npos = -1;
void string::erase(size_t pos, size_t len)
{
assert(_size > pos);
if(len > _size - pos)
{
_str[pos] = '\0';
_size = pos;
}
else
{
strcpy(_str + pos, _str + pos + len);
_size -= len;
}
}
14.🍁find函数实现
🍃size_t find(char ch, size_t pos);
size_t string::find(char ch, size_t pos)
{
assert(_size > pos);
int index = pos;
// npos在前面有定义
while (index < _size)
{
if (_str[index] == ch)
return index;
++index;
}
return npos;
}
🍃size_t find(const char* str, size_t pos);
size_t string::find(const char* str, size_t pos)
{
char* p = strstr(_str + pos, str);
return p - _str;
}
15.🍁swap函数的实现
void string::swap(string& s)
{
std::swap(_str,s._str);
std::swap(_size,s._size);
std::swap(_capacity,s._capacity);
}
16.🍁substr的实现
string string::substr(size_t pos, size_t len)
{
if(len >= _size - pos)
{
string tmp(_str + pos);
return tmp;
}
else
{
string tmp;
tmp.reserve(len);
for(int i = 0;i < len;++i)
{
tmp._str[i] = _str[pos + i];
}
// 这么些也可以
// memcpy(tmp._str,_str + pos,len);
tmp._size = len;
return tmp;
}
}
17.🍁运算符重载
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;
bool string::operator<(const string& s) const
{
return strcmp(_str, s._str) < 0;
}
bool string::operator>(const string& s) const
{
return !(_str < s._str);
}
bool string::operator<=(const string& s) const
{
return _str < s._str || _str == s._str;
}
bool string::operator>=(const string& s) const
{
return !(_str < s._str) || _str == s._str;
}
bool string::operator==(const string& s) const
{
return strcmp(_str, s._str) == 0;
}
bool string::operator!=(const string& s) const
{
return !(_str == s._str);
}
18.🍁>>重载函数和<<重载函数
🍃>>重载函数
由于流提取需要将整个值改变,所以需要清空原本的值,所以引用函数clear()
。
由于流提取会自动忽略空格和换行,所以我们用get()
函数来解决流提取问题
void string::clear()
{
_str[0] = '\0';
_size = 0;
}
istream& My_string::operator>> (istream& is, string& str)
{
str.clear();
char buff[128];
char ch = is.get();
int i = 0;
while (ch != ' ' && ch != '\n')
{
buff[i] = ch;// 临时变量,能够快速生成
++i;
if (i == 127)// 当buff已经满了,进行+=操作
{
buff[i] = '\0';
str += buff;
i = 0;// 记得i要置为0
}
ch = is.get();// 提取下一个字符
}
if (i > 0)// 当还有字符没有进行插入时,继续进行+=操作
{
buff[i] = '\0';
str += buff;
}
return is;
}
🍃<<重载函数
ostream& My_string::operator<<(ostream& os,const string& str)
{
for (size_t i = 0; i < str.size(); i++)
{
os << str[i];
}
return os;
}
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