C++心决之stl中那些你不知道的秘密(string篇)

3.5 string类的模拟实现

//string.h
#pragma once
#include<iostream>
#include<assert.h>
using namespace std;
namespace mystr {class string{public://迭代器, 因为字符串底层内存连续, 所以可以简单的定义成指针typedef char* iterator;typedef const char* const_iterator;//配合范围for循环iterator begin() { return _str; }iterator end() { return _str + _size; }//兼容常量字符串const_iterator begin() const { return _str; }const_iterator end() const { return _str + _size; }//string();string(const char* str = "");string(const string& s);string& operator=(string temp) { swap(temp); return *this; }~string() { delete[] _str; _str = nullptr; _size = _capacity = 0; }//返回C语言字符数组const char* c_str() const { return _str; }size_t size() const { return _size; }char& operator[](size_t pos) { assert(pos < _size); return _str[pos]; }const char& operator[](size_t pos) const{ assert(pos < _size); return _str[pos]; }//重置大小void reserve(size_t n);void push_back(char ch) { insert(_size, ch); }void append(const char* str) { insert(_size, str); }string& operator+=(char ch) { insert(_size, ch); return *this; }string& operator+=(const char* str) { insert(_size, str); return *this; };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) {for (size_t i = pos; i < _size; i++) if (_str[i] == ch) return i;return npos;}size_t find(const char* str, size_t pos = 0) { return strstr(_str + pos, str) - _str; }void swap(string& s);string substr(size_t pos = 0, size_t len = npos);bool operator<(const string& s) const { return strcmp(_str, s._str) < 0; }bool operator>(const string& s) const { return !(*this <= s); }bool operator<=(const string& s) const { return !(*this > s); }bool operator>=(const string& s) const { return !(*this < s); }bool operator==(const string& s) const {return strcmp(_str, s._str) == 0; }bool operator!=(const string& s) const { return !(*this == s); }void clear() { _str[0] = '\0'; _size = 0; }private:char* _str;size_t _size;size_t _capacity;//一般static变量的定义要放在类外, 整型是特例const static size_t npos = -1;};void swap(string& s1, string& s2);istream& operator>>(istream& ci, string& s);ostream& operator<<(ostream& co, string& s);
}

//string.cpp
#include "string.h"
namespace mystr {string::string(const char* str):_size(strlen(str)) {_str = new char[_size + 1];_capacity = _size;strcpy(_str, str);}string::string(const string& s) {string temp(s._str);swap(temp);}void string::reserve(size_t n) {if (_capacity < n) {char* temp = new char[n + 1];strcpy(temp, _str);delete[] _str;_str = temp;_capacity = n;}}void string::insert(size_t pos, char ch) {assert(pos <= _size);if (_size == _capacity) {size_t newcapacity = _capacity == 0 ? 4 : 2 * _capacity;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 - 1) _str[end] = _str[end - len], --end;memcpy(_str + pos, str, len);_size += len;}void string::erase(size_t pos, size_t len) {if (len > _size - pos) _str[pos] = '\0', _size = pos;else strcpy(_str + pos, _str + pos + len), _size -= len;}void string::swap(string& s) {char* temp = _str;_str = s._str;s._str = temp;std::swap(_size, s._size);}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 = pos; i < pos + len; i++) sub += _str[i];return sub;}}void swap(string& s1, string& s2){ s1.swap(s2); }istream& operator>>(istream& ci, string& s) {s.clear();char ch = ci.get();while (ch != ' ' && ch != '\n') s += ch, ch = ci.get();return ci;}ostream& operator<<(ostream& co, string& s) {for (size_t i = 0; i < s.size(); i++) co << s[i];return co;}
}

//test.cpp
#include "string.h"
namespace mystr {void test1() {string s1 = "1111";string s2 = s1;cout << s1.c_str() << endl << s2.c_str() << endl;cout << s1.size() << endl;}void test2() {string s1 = "111";string s2 = "222222";s1 = s2;cout << s1.c_str() << endl;}void test3() {string s1 = "111222333";for (auto& i : s1) i += 3;cout << s1.c_str() << endl;const string s2 = "111222333";for (auto& i : s2) cout << i;cout << endl;for (size_t i = 0; i < s1.size(); i++) cout << (s1[i] += 2);cout << endl;}void test4() {string s1 = "sadfsf";s1.insert(2, '-');cout << s1.c_str() << endl;s1.insert(0, '-');cout << s1.c_str() << endl;s1.insert(2, "11111");cout << s1.c_str() << endl;s1.insert(0, "222222");cout << s1.c_str() << endl;}void test5() {string s1 = "asgfidsgf";s1.push_back('-');cout << s1.c_str() << endl;s1.append("=====");cout << s1.c_str() << endl;s1 += 'w';cout << s1.c_str() << endl;s1 += "0000";cout << s1.c_str() << endl;s1.erase(10);cout << s1.c_str() << endl;s1.erase(7, 100);cout << s1.c_str() << endl;s1.erase(3, 2);cout << s1.c_str() << endl;s1.erase(0);cout << s1.c_str() << endl;}void test6() {string s1 = "ksjfghks";cout << s1.find('h', 2) << endl;cout << s1.find("ghk", 2) << endl;cout << s1.find("ghksgs", 2) << endl;}void test7(){string s1 = "sggsdsdf";string s2 = "sdgfrgdb";cout << s1.c_str() << endl;cout << s2.c_str() << endl;swap(s1, s2);cout << s1.c_str() << endl;cout << s2.c_str() << endl;s1.swap(s2);cout << s1.c_str() << endl;cout << s2.c_str() << endl;string s3 = s1.substr(2, 5);cout << s3.c_str() << endl;}void test8() {string s1, s2;cin >> s1 >> s2;cout << s1 << endl << s2 << endl;}
}
int main() {mystr::test8();return 0;
}