#pragma once
#define _CRT_SECURE_NO_WARNINGS 1
#include<iostream>
#include<assert.h>
using namespace std;
namespace liu
{class string{public:using iterator = char*;using const_iterator = const char*;//string();//无参构造 string(const string& s);//拷贝构造string(const char* str="");//有参构造~string();//析构char& operator[](size_t i){assert(i < _size);return _str[i];}const char& operator[](size_t i)const{assert(i < _size);return _str[i];}size_t size()const{return _size;}const char* c_str()const//c_str函数，返回_str{return _str;}iterator begin(){return _str;}iterator end(){return _str+_size;}const_iterator begin()const{return _str;}const_iterator end()const{return _str + _size;}void clear(){_str[0] = '\0';_size = 0;}void reserve(size_t n);void push_back(char ch);void append(const char* ch);string& operator+=(char ch);string& operator+=(const char* ch);void insert(size_t pos,char ch);void insert(size_t pos,const char* ch);void erase(size_t pos,size_t len=npos);size_t find(char ch,size_t pos=0);size_t find(const char* ch,size_t pos=0);string substr(size_t pos = 0, size_t len = npos)const;string& operator=(string s);void swap(string& s);private:char* _str=nullptr;size_t _size=0;size_t _capacity=0;public://c++的特殊处理static const size_t npos=-1;};void swap(string& s1, string& s2);bool operator==(const string& lhs, const string& rhs);bool operator!=(const string& lhs, const string& rhs);bool operator<(const string& lhs, const string& rhs);bool operator>(const string& lhs, const string& rhs);bool operator<=(const string& lhs, const string& rhs);bool operator>=(const string& lhs, const string& rhs);ostream& operator<<(ostream& os,const string& str);istream& operator>>(istream& is, string& str);istream& getline(istream& is, string& str,char delim='\n');}
#include"string.h"namespace liu
{//const size_t string:: npos = -1;/*string::string():_str(new char[1] {'\0'}), _size(0), _capacity(0){}*/string::string(const char* str)//:_str(new char[strlen(str)+1])//出去字符串的空间，还要保留一个'\0'的空间，所以开辟的空间要加1//,_size(strlen(str))//,_capacity(strlen(str)):_size(strlen(str)){_str = new char[_size + 1];_capacity = _size;strcpy(_str, str);}/*string::string(const string& s){_str = new char[s._capacity+1];strcpy(_str,s._str);_size = s._size;_capacity = s._capacity;}*/string::string(const string& s){string tmp(s._str);swap(tmp);}string::~string(){delete[] _str;_str = nullptr;_size = 0;_capacity = 0;}void string::reserve(size_t n){if (n>_capacity){cout << "reserve:" << n << endl;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;*/insert(_size,ch);}void string::append(const char* ch){/*size_t len = strlen(ch);if (_size+len>_capacity){size_t NewCapacity = 2 * _capacity;if (NewCapacity < _size + len)NewCapacity = _size + len;reserve(NewCapacity);}strcpy(_str + _size, ch);_size += len;*/insert(_size,ch);}string& string::operator+=(char ch){push_back(ch);return *this;}string& string::operator+=(const char* ch){append(ch);return *this;}void string::insert(size_t pos, char ch){if (_size == _capacity){reserve(_capacity == 0 ? 4 : _capacity * 2);}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* ch){assert(pos<=_size);size_t len = strlen(ch);if (_size + len > _capacity){size_t NewCapacity = 2 * _capacity;if (NewCapacity < _size + len)NewCapacity = _size + len;reserve(NewCapacity);} size_t end = _size+len;while (end>pos+len-1 ){_str[end] = _str[end-len];--end;}for (size_t i=0;i<len;i++){_str[pos + i] = ch[i];}_size += len;}void string::erase(size_t pos, size_t len){assert(pos<_size);if (len>_size-pos){_str[pos] = '\0';_size = pos;}else{size_t end = pos + len;while (end<=_size){_str[end - len] = _str[end];++end;}_size -= len;}}size_t string::find(char ch, size_t pos){assert(pos<_size);for (size_t i=pos;i<_size;i++){if (ch==_str[i]){return i;}}return npos;}size_t string::find(const char* ch, size_t pos){const char* ptr = strstr(_str+pos,ch);if (ptr==nullptr){return npos;}else{return ptr - _str;}}string string::substr(size_t pos , size_t len )const{if (len>(_size-pos)){len = _size - pos;}liu::string sub;sub.reserve(len);for (size_t i=0;i<len;i++){ sub += _str[pos + i];}return sub;}//传统写法//string& string::operator=(const string& s)//{// if (this != &s)// {// delete[] _str;// _str = new char[s._capacity + 1];// strcpy(_str, s._str);// _size = s._size;// _capacity = s._capacity;// }// return *this;//}string& string::operator=( string s){/*if (this != &s){ string tmp(s._str);swap(tmp);}*/swap(s);return *this;}void string::swap(string& s){std::swap(_str,s._str);std::swap(_size,s._size);std::swap(_capacity,s._capacity);}//void swap(string& s1, string& s2){s1.swap(s2);}bool operator==(const string& lhs, const string& rhs){return strcmp(lhs.c_str(),rhs.c_str())==0;}bool operator!=(const string& lhs, const string& rhs){return !(lhs == rhs);}bool operator<(const string& lhs, const string& rhs){return strcmp(lhs.c_str(),rhs.c_str())<0;}bool operator>(const string& lhs, const string& rhs){return !(lhs < rhs || lhs == rhs);}bool operator<=(const string& lhs, const string& rhs){return lhs < rhs || lhs == rhs;}bool operator>=(const string& lhs, const string& rhs){return !(lhs < rhs);}ostream& operator<<(ostream& os, const string& str){//os<<"\"";//os << '"';for (size_t i=0;i<str.size();i++){cout << str[i];}return os;}istream& operator>>(istream& is, string& str){str.clear();//str.reserve(1024);int i = 0;char buff[256];char ch;ch = is.get();while (ch!=' '&&ch!='\n'){buff[i++] = ch;if (i==255){buff[i] = '\0';str += buff;i = 0;}ch = is.get();}if (i>0){buff[i] = '\0';str += buff;}return is;}istream& getline(istream& is, string& str, char delim){str.clear();int i = 0;char buff[256];char ch;ch = is.get();while (ch != delim){buff[i++] = ch;if (i == 255){buff[i] = '\0';str += buff;i = 0;}ch = is.get();}if (i > 0){buff[i] = '\0';str += buff;}return is;}}
构造函数：
string(const char* str="")//当实例化时，没有给参数，就使用这里的缺省参数，这个参数就相当于给对象赋值了一个'\0':_size(strlen(str))
{_capacity = _size;_str = new char[_size + 1];strcpy(_str,str);
}
