string的模拟实现
- string的模拟实现（重点）
string的模拟实现（重点）
头文件：
#pragma once
#define _CRT_SECURE_NO_WARNINGS 1#include<iostream>
#include<string>
#include<assert.h>
using namespace std;namespace bit
{class string{public:typedef char* iterator;typedef const char* const_iterator;iterator begin(){return _str;}iterator end(){return _str + _size;}const_iterator begin() const{return _str;}const_iterator end() const{return _str + _size;}/*string():_str(new char[1]{'\0'}),_size(0),_capacity(0){}*/// 短小频繁调用的函数，可以直接定义到类里面，默认是inlinestring(const char* str = ""){_size = strlen(str);// _capacity不包含\0_capacity = _size;_str = new char[_capacity + 1];strcpy(_str, str);}// 深拷贝问题// // s2(s1)//string(const string& s)//{// _str = new char[s._capacity + 1];// strcpy(_str, s._str);// _size = s._size;// _capacity = s._capacity;//}// 深拷贝问题的优化// 现代写法(非常重要）void swap(string& s){std::swap(_str, s._str);std::swap(_size, s._size);std::swap(_capacity, s._capacity);}string(const string& s){string tmp(s._str);swap(tmp)}// s2 = s1// s1 = s1string& operator=(const string& s){if (this != &s){string tmp(s._str);swap(tmp);}return *this;}~string(){if (_str){delete[] _str;_str = nullptr;_size = _capacity = 0;}}const char* c_str() const{return _str;}void clear()//不释放空间，清数据{_str[0] = '\0';_size = 0;}size_t size() const{return _size;}size_t capacity() const{return _capacity;}char& operator[](size_t pos){assert(pos < _size);return _str[pos];}const char& operator[](size_t pos) const{assert(pos < _size);return _str[pos];}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, size_t len = npos);private:char* _str = nullptr;size_t _size = 0;size_t _capacity = 0;static const size_t npos = -1;//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);ostream& operator<<(ostream& out, const string& s);istream& operator>>( istream& in, string& s);}
源文件：
#include"string.h"namespace bit
{const size_t string::npos = -1;void test_string1(){string st;string st1("hh");cout << st.c_str() << endl;cout<< st1.c_str() << endl;string s1("hello world");string::iterator it = s1.begin();while (it != s1.end()){cout << *it;it++;}for (auto ch : s1 ){cout << ch << " ";}cout << endl;cout << endl;}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;++_size;_str[_size] = '\0';}string& string::operator+=(char ch){push_back(ch);return (*this);}string& string::operator+=(const char* str){append(str);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;}void string::insert(size_t pos, char ch){assert(pos <= _size);if (_size == _capacity){reserve(_capacity == 0 ? 4 : _capacity * 2);}// 挪动数据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* s){assert(pos <= _size);size_t len = strlen(s);if (_size + len > _capacity){// 大于2倍，需要多少开多少，小于2倍按2倍扩reserve(_size + len > 2 * _capacity ? _size + len : 2 * _capacity);}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] = 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];}_str -= 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(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)//取子串{assert(pos < _size);if (len > _size - pos){len = _size - pos;}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.c_str(), s2.c_str()) == 0;}bool operator<(const string& s1, const string& s2){return strcmp(s1.c_str(), s2.c_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 !(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];char ch;in >> ch;int i = 0;ch = in.get();while (ch != ' ' && ch != '\n'){buff[i++] = ch;if (i == N - 1){buff[i] = '\0';s += buff;i = 0;}ch = in.get();//*}if (i > 0){buff[i] = '\0';s += buff;}return in;}
}string的模拟实现