目录

1.模拟实现string

1.string基本属性和大体框架

 2.基本函数

2.1size（）

 2.2 []

2.3 begin() 和end()

 2.4capacity（）

2.5  reserve

2.6push_back

2.7 append

2.8 +=

2.9insert

2.10find

2.11substr

2.12 =

2.12  <

2.13   >

2.14 <=

2.15 >=

2.16 ==

2.17 !=

2.19  <<

2.20  >>

3.完整代码

string.h

string.c

---

1.模拟实现string

1.string基本属性和大体框架

#pragma once
#define _CRT_SECURE_NO_WARNINGS 1
#include<iostream>
#include <string>
#include<assert.h>
namespace String
{class string{public:
//默认构造string(const char* str=""){_size = strlen(str);//capacity不包含"\0"_capacity = _size;_str = new char[_capacity + 1];strcpy(_str, str);}
//析构函数~string(){delete[] _str;_str = nullptr;_size = _capacity = 0;}//基本变量private:char* _str;size_t _size;size_t _capacity;};

 2.基本函数

2.1size（）

内容个数

//模拟size()size_t size(){return _size;}		

 2.2 []

访问元素

#//模拟[] 普通引用和const引用两个版本char& operator[](size_t pos){assert(pos < _size);return _str[pos];}const char& operator[](size_t pos) const{assert(pos < _size);return _str[pos];}

2.3 begin() 和end()

简单用typedef重定义char* 来模拟iterator获取begin（）和end（）

	 typedef char* iterator;iterator begin(){return _str;}iterator end(){return _str + _size;}

 2.4capacity（）

获取容量

size_t capacity() const
{return _capacity;
}

2.5  reserve

调整空间

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

2.6push_back

尾插字符

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

2.7 append

尾插支付串

void  string::append(const char* str){size_t len = strlen(str);
//大于二倍就要多少开多少，低于二倍按二倍开if (_size + len > _capacity){reserve(_size + len > 2 * _capacity ? _size + len : 2 * _capacity);}strcpy(_str + _size, str);_size += len;}

2.8 +=

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

2.9insert

在指定位置插入字符或字符串

void string::insert(size_t pos, char ch)
{if (_size == _capacity){reserve(_capacity == 0 ? 4 : _capacity * 2);}assert(pos <= _size);size_t end = _size;while (end > pos){_str[end ] = _str[end-1];--end;}_str[pos] = ch;++_size;
}void string::insert(size_t pos, const char* s)
{assert(pos <= _size);size_t len = strlen(s);
if(len==0)
return;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 - len] = _str[end];--end;}for (size_t i = 0; i < len; i++){_str[pos + i] = s[i];}_size += len;
}

2.10 erase

删除指定位置元素

void string::erase(size_t pos, size_t len)
{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;}
}

2.10find

查找字符或字符串

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

2.11substr

提取字符重新构建string类

//深拷贝
string(const string&s)
{_str = new char[s._capacity + 1];strcpy(_str, s._str);_size = s._size;_capacity = s._capacity;
}string string::substr(size_t pos, size_t len )
{assert(pos < _size);//len答疑剩余有效长度更新一下if (len > _size - len){len = _size - len;}string sub;sub.reserve(len);for (size_t i = 0; i < len; i++){sub += _str[pos + i];}return sub;
}

2.12 =

 //s2=s1string& operator=(const string& s){//避免s1=s1出现释放了_strif(this!=&s)delete[] _str;_str = new char[s._capacity];strcpy(_str, s._str);_size = s._size;_capacity = s._capacity;return *this;}

2.12  <

bool operator<(const string& s1, const string& s2)
{return strcmp(s1.Get_str(), s2.Get_str())<0;
}

2.13   >

bool operator>(const string& s1, const string& s2)
{return !(s1 <= s2);
}

2.14 <=

bool operator<=(const string& s1, const string& s2)
{return s1 < s2 || s1 == s2;}

2.15 >=

bool operator>=(const string& s1, const string& s2)
{return !( s1 < s2);
}

2.16 ==

bool operator==(const string& s1, const string& s2)
{return strcmp(s1.Get_str(), s2.Get_str()) ==0;
}

2.17 !=

bool operator!=(const string& s1, const string& s2)
{return !(s1 == s2);
}

2.18 clear

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

2.19  <<

	ostream& operator<<(ostream& out, const string& s){for (auto ch : s){out << ch;}return out;}

2.20  >>

istream& operator >> (istream& in, string& s){char ch;ch = in.get();	while (ch != ' ' && ch != '\n'){s += ch;ch = in.get();}return in;}

3.完整代码

string.h

#pragma once
#define _CRT_SECURE_NO_WARNINGS 1
#include<iostream>
#include <string>
#include<assert.h>
namespace String
{class string{public://s1(s)string(const string&s){_str = new char[s._capacity + 1];strcpy(_str, s._str);_size = s._size;_capacity = s._capacity;}string(const char* str=""){_size = strlen(str);//capacity不包含"\0"_capacity = _size;_str = new char[_capacity + 1];//+1位置给'\0'strcpy(_str, str);}~string(){delete[] _str;_str = nullptr;_size = _capacity = 0;}//短小频繁，默认inline//获取_strchar* Get_str() const{return _str;}//模拟size()size_t size(){return _size;}//模拟实现capacity()size_t capacity() const{return _capacity;}//简单用typedef重定义char* 来模拟iterator获取begin（）和end（）typedef char* iterator;iterator begin() const{return _str;}iterator end() const{return _str + _size;}//模拟[] 普通引用和const引用两个版本char& operator[](size_t pos){assert(pos < _size);return _str[pos];}const char& operator[](size_t pos) const{assert(pos < _size);return _str[pos];}//s2=s1string& operator=(const string& s){//避免s1=s1出现释放了_strif (this != &s)delete[] _str;_str = new char[s._capacity];strcpy(_str, s._str);_size = s._size;_capacity = s._capacity;return *this;}void clear(){_str[0] = '\0';_size = 0;}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* s);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;size_t _size;size_t _capacity;static const size_t npos;};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);bool operator!=(const string& s1, const string& s2);istream& operator>>(istream& out, const string& s);istream& operator<<(istream& in, string& s);
}

string.c

//text.cppusing namespace std;
#include"FileName.h"
namespace String
{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 : _capacity * 2);}_str[_size++] = ch;_str[_size] = '\0';}string& string::operator+=(char ch){push_back(ch);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;}string& string::operator+=(const char* str){append(str);return *this;}void string::insert(size_t pos, char ch){if (_size == _capacity){reserve(_capacity == 0 ? 4 : _capacity * 2);}assert(pos <= _size);size_t end = _size;while (end > pos){_str[end ] = _str[end-1];--end;}_str[pos] = ch;++_size;}void string::insert(size_t pos, const char* s){assert(pos <= _size);size_t len = strlen(s);if (len == 0)return;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 - len] = _str[end];--end;}for (size_t i = 0; i < len; i++){_str[pos + i] = s[i];}_size += len;}void string::erase(size_t pos, size_t len){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 ){for (size_t i = pos; 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;}else {return ptr - _str;}}string string::substr(size_t pos, size_t len ){assert(pos < _size);//len答疑剩余有效长度更新一下if (len > _size - len){len = _size - len;}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.Get_str(), s2.Get_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.Get_str(), s2.Get_str()) ==0;}bool operator!=(const string& s1, const string& s2){return !(s1 == s2);}ostream& operator<<(ostream& out, const string& s){for (auto ch : s){out << ch;}return out;}istream& operator >> (istream& in, string& s){s.clear();const int N = 256;char buff[N];int i = 0;char ch;//in >> ch ;ch = in.get();	while (ch != ' ' && ch != '\n'){buff[i++] = ch;if (i == N - 1){buff[i] = '\0';s += buff;i = 0;}ch = in.get();}return in;}
}
int main()
{return 0;
}