目录
1、什么是STL
STL6大组件:仿函数、算法、容器、空间配置器、迭代器、配接器
推荐文档（必须学会看文档）
2、string常用接口
a、初始化
1、什么是STL
标准模板库 STL（Standard Template Library），主要是数据结构和算法的框架，是模板库的一部分,STL是一个规范，是一个实现要求，但是并没有要求实现细节.
STL6大组件:仿函数、算法、容器、空间配置器、迭代器、配接器
推荐文档（必须学会看文档）
string - C++ Reference (cplusplus.com)
https://legacy.cplusplus.com/reference/string/string/?kw=string
2、string常用接口
a、初始化
哎呀，这部分，再写一遍很没有必要，所以就不写了。毕竟文档介绍的已经足够清晰，不会就查看文档，单词不会就查。主要的是要懂得底层的实现，懂得底层实现的细节，就能够更好的使用。而不仅仅只是一个接口工程师。
string - C++ Reference (cplusplus.com)https://legacy.cplusplus.com/reference/string/string/?kw=string
string提供的接口非常多，也很冗余。但是不影响，只要用主要的几个就好。
返回值不同不构成函数重载
3、string底层简单实现
#define _CRT_SECURE_NO_WARNINGS 1
#pragma once
#include<iostream>
#include<assert.h>
#include<string.h>
using namespace std;namespace bit
{class string{friend ostream& operator<<(ostream& _cout, const bit::string& s);friend istream& operator>>(istream& _cin, bit::string& s);public:typedef char* iterator;typedef const char* const_iterator;public:void swap( string& s){std::swap(_str,s._str);std::swap(_size,s._size);std::swap(_capacity,s._capacity);}//s1("xxx")string(const char* str = ""){_size = strlen(str);_capacity = _size;_str = new char[_capacity + 1];strcpy(_str,str);}//s2(s1)拷贝string(const string& s) {/* _size = s._size;_capacity = _size;_str = new char[_capacity + 1];strcpy(_str,s._str);*///这里的将s1交s2，同理，也可以直接使用swap交换//但是s是一个const，需要拷贝一份非conststring tmp(s._str);swap(tmp);}//s2 = s1string& operator=( string& s){/*_size = s._size;_str = new char[_size];strcpy(_str,s._str);_capacity = s._capacity;*/string tmp(s);swap(tmp);return *this;}//析构~string(){delete[] _str;_size = _capacity = 0;}const char* c_str()const{return _str;}//// iteratoriterator begin(){return _str;}iterator end(){return _str + _size;}const_iterator begin() const{return _str;}const_iterator end() const{return _str + _size;}const char& operator[]( size_t pos)const{assert(pos < _size);return _str[pos];}char& operator[]( size_t pos){assert(pos < _size);return _str[pos];}///modifystring& push_back(char c){/* if (_size == _capacity ){char* tmp = new char[_capacity = _capacity == 0 ? 4 : _capacity * 2];}_str[_size] = c;++_size;*/insert(_size,c);return *this;}string& operator+=(char c){insert(_size,c);return *this;}string& operator+=(const char* str){insert(_size, str);return *this;}string& append(const char* str){insert(_size,str);return *this;}void clear(){delete[] _str;_capacity = _size = 0;_str = nullptr;}///// capacitysize_t size()const{return _size;}size_t capacity()const{return _capacity;}bool empty()const{return _size == 0;}void resize(size_t n, char ch = '\0'){if (n <= _size){_str[n] = '\0';_size = n;}else{reserve(n);for (size_t i =_size;i<n;++i){_str[i] = ch;}_str[n] = '\0';_size = n;}}void reserve(size_t n){if (n > _capacity ){char* tmp = new char[n + 1];strcpy(tmp,_str);delete[] _str;_str = tmp;_capacity = n;}}/// 返回c在string中第一次出现的位置size_t find(char c) const{size_t i = 0;while (i < _size){if (_str[i] == c){return i;}++i;}}// 返回子串s在string中第一次出现的位置size_t find(const char* s) const{char* cur = strstr(this->_str,s);size_t len = cur - _str;return len;}// 在pos位置上插入字符c/字符串str，并返回该字符的位置size_t insert(size_t pos, char c){assert(pos <= _size );if (_size <= _capacity ){//char* tmp = new char[_capacity == 0 ? 4 : _capacity * 2];//扩容两倍reserve(_capacity == 0 ? 4 : _capacity * 2);}size_t end = _size + 1;//把\0也往后移动while(end > pos)//当end到pos下一个位置，正好把pos位置往后移动{_str[end] = _str[end - 1];--end;}_str[pos] = c;_size++;return pos;}void insert(size_t pos, const char* str){assert(pos <= _size);if (strlen(str ) + _size > _capacity){reserve(_size + strlen(str));}//往后移动len位置，插入strsize_t len = strlen(str);size_t end = len + _size;while (end >= pos + len ){_str[end] = _str[end - len];--end;}//不能把\0粘贴进来strncpy(_str + pos, str,len);_size += len;}// 删除pos位置上的元素，并返回该元素的下一个位置size_t erase(size_t pos, size_t len = 1){assert(pos < _size);//删除pos位置以后的值//如果n等于超过size，删完，不管//小于，往前挪动覆盖即可if ( len >= _size - pos ){_str[len] = '\0';_size = pos;}else{//从pos位置开始，往后len个位置，往前覆盖strcpy(_str + pos, _str + pos + len);_size -= len;}return pos + 1;}void print(){for (auto e : *this){cout << e ;}cout << endl;}public:static const int npos;//声明private:char* _str;size_t _capacity;size_t _size;};//创建const int string::npos = -1;//relational operators直接利用strcmp函数返回值,而不是自己遍历对比bool operator<(const string& s1, const string& s2){int ret = strcmp(s1.c_str(), s2.c_str()) ;return ret < 0;}bool operator>(const string& s1, const string& s2){int ret = strcmp(s1.c_str(), s2.c_str());return ret > 0;}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){int ret = strcmp(s1.c_str(), s2.c_str()) ;return ret == 0;}bool operator!=(const string& s1, const string& s2){return !(s1 == s2);}ostream& operator<<(ostream& _cout, const bit::string& s){for (size_t i = 0; i < s.size();++i){_cout << s.c_str()[i];}return _cout;}istream& operator>>(istream& _cin, bit::string& s){for (size_t i = 0; i<s.size();++i){_cin >> s._str[i];}return _cin;}void test1(){string s0;string s1("hello world");const string s2("hello Linux");s0 = s1;const string s3 = s2;for (auto e : s3){cout << e;}cout << endl;}void test2(){string s("hello world");s.reserve(5);cout << s.capacity() << endl;;s.reserve(20);cout << s.capacity() << endl;s.print();}void test3(){string s("hello world");//s.resize(5);//s.print();//cout << s.size() << endl;s.resize(30,'x');s.print();cout << s.size() << endl;cout << s[29] << endl;}void test4(){string s1("abc");string s2("def");cout << (s1 == s2) << endl;cout << (s1 != s2) << endl;cout << (s1>s2) << endl;cout << (s1 <= s2) << endl;cout << (s1 >= s2) << endl;}void test5(){string s1("abcxxxxxxxxxxxxxxxxxxxxx");s1.erase(1,100);// s1.erase(1);s1.print();}void test6(){string s("hello world");//s.insert(11,"xxxxx");s.insert(11,"abbbb");cout << s.capacity() << endl;cout << s.size() << endl;s.print();}void test7(){string s1("aaabbbccc");//size_t add = s1.find('b');size_t add = s1.find("ccc");cout << add << endl;}void test8(){string s("hello world");s.push_back('a');s.append("xxxx");s += 'w';s += "oooooo";//cout << s << endl;s.print();}void test9 (){//string s("hello world ");//cout << s;string s1;//int a;//cin >> a;//cout << a;//"hello" >> s1.c_str;cout<<s1;}};
