目录
string类实现
1.构造函数（三种）
2.c_str()函数
3.operator[] 重载
4.size()函数实现
5.迭代器
6.reserve()函数实现
7.push_back()函数实现
8.append()函数实现
9.operator+=实现
10.insert() 实现
11.erase()函数实现
12.find()函数实现
13.swap()函数实现
14.substr()函数实现
15.运算符重载比大小
16.clear
17.流插入 流提取实现
18.析构函数
补充修改
1.push_back优化
2.append优化
3.insert函数另外一种方法
string类实现
我们采用声明和定义分离的方式
首先是.h文件
//
// string.hpp
// String
//
// Created by 南毅 on 2024/5/8.
//#ifndef string_hpp
#define string_hpp#endif /* string_hpp */
#include <iostream>
using namespace std;
#include <assert.h>
#include <string.h>namespace nanyi{class String{private:char* _str;size_t _size;size_t _capacity;const static size_t npos;public:typedef char* iterator;typedef const char* const_iterator;//s构造函数、初始化列表//拷贝构造String(const char* str = "");String();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;iterator begin();iterator end();const_iterator begin() const;const_iterator end() 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();};istream& operator>> (istream& is, string& str);ostream& operator<< (ostream& os, const string& str);
}
1.构造函数（三种）
//构造函数
String::String(const char* str):_size(strlen(str))
{_capacity = _size;_str = new char[_size + 1];strcpy(_str, str);
}
//默认构造
String::String(){_str = new char[1]{'\0'};_size = _capacity = 0;
}//拷贝构造
String::String(const String& s)
{_str = new char[s._capacity + 1];strcpy(_str, s._str);_size = s._size;_capacity = s._capacity;}2.c_str()函数
因为C形式字符串是内置类型，所以使用cout打印时编译器会自动识别类型，相当于使用%s进行打印字符串，只需要返回字符串数组首字符地址即可
const char* String:: c_str() const {return _str;
}3.operator[] 重载
可以以数组的形式，通过下标访问数据
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];
}4.size()函数实现
size_t String::size() const
{return _size;
}
5.迭代器
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;
}6.reserve()函数实现
void String::reserve(size_t n){char* tmp = new char[n+1];strcpy(tmp, _str);delete [] _str;_str = tmp;_capacity = n;
}7.push_back()函数实现
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++;
}8.append()函数实现
void String::append(const char* str){size_t len = strlen(str);if (_size + len > _capacity) {reserve(_size + len);}strcpy(_str + _size, str);_size += len;
}9.operator+=实现
//+=一个字符
String& String::operator+=(char ch){push_back(ch);return *this;
}
//+=一个字符串
String& String::operator+=(const char* str){append(str);return *this;
}10.insert() 实现
void String::insert(size_t pos, char ch){assert(pos <= _size);if (_size == _capacity) {size_t newcapacity = _capacity == 0? 4 : _capacity*2;reserve(newcapacity);}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);}size_t end = _size + len;while (end >= pos + len) {_str[end] = _str[end-len];end--;}memcpy(_str + pos, str, len);_size += len;
}11.erase()函数实现
void String::erase(size_t pos, size_t len){assert(pos <= _size);if (len >= _size - pos) {_str[pos] = '\0';_size = pos;}else{strcpy(_str + pos, _str + pos + len);_size -= len;}
}12.find()函数实现
size_t String::find(char ch, size_t pos){for (size_t i = 0; 0 < _size; i++) {if (_str[i] == ch) {return i;}}return npos;
}size_t String::find(const char* str, size_t pos){char* p = strstr(_str + pos,str);return p - _str;
}13.swap()函数实现
void String::swap(String& s){std::swap(_str, s._str);std::swap(_size, s._size);std::swap(_capacity, s._capacity);
}14.substr()函数实现
String String::substr(size_t pos, size_t len){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;}}15.运算符重载比大小
bool String::operator<(const String& s) const{return strcmp(_str, s._str) < 0;
}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 !(*this == s);}
16.clear
void String::clear(){_str[0] = '\0';_size = 0;}17.流插入 流提取实现
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;
}18.析构函数
//析构函数
String::~String(){delete[] _str;_str = nullptr;_capacity = _size = 0;}补充修改
1.push_back优化
void String::push_back(char ch){insert(_size, ch);
}2.append优化
void String::append(const char* str){insert(_size, str);
}3.insert函数另外一种方法
void String::insert(size_t pos, char ch){assert(pos <= _size);if (_size == _capacity) {size_t newcapacity = _capacity == 0? 4 : _capacity*2;reserve(newcapacity);}size_t end = _size;while (end >= (int)pos){_str[end + 1] = _str[end];--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;}memcpy(_str + pos, str, len);_size += len;
}
