当前位置：首页 > news >正文

C++STL简介（二）

news 2025/8/15 15:29:33

1.模拟实现string

1.string基本属性和大体框架

2.基本函数

2.1size（）

2.2 []

2.3 begin() 和end()

2.4capacity（）

2.5 reserve

2.6push_back

2.7 append

2.8 +=

2.9insert

2.10find

2.11substr

2.12 =

2.12 <

2.13 >

2.14 <=

2.15 >=

2.16 ==

2.17 !=

2.19 <<

2.20 >>

3.完整代码

string.h

string.c

1.模拟实现string

1.string基本属性和大体框架

#pragma once
#define _CRT_SECURE_NO_WARNINGS 1
#include<iostream>
#include <string>
#include<assert.h>
namespace String
{class string{public:
//默认构造string(const char* str=""){_size = strlen(str);//capacity不包含"\0"_capacity = _size;_str = new char[_capacity + 1];strcpy(_str, str);}
//析构函数~string(){delete[] _str;_str = nullptr;_size = _capacity = 0;}//基本变量private:char* _str;size_t _size;size_t _capacity;};

2.基本函数

2.1size（）

内容个数

//模拟size()size_t size(){return _size;}

2.2 []

访问元素

#//模拟[] 普通引用和const引用两个版本char& operator[](size_t pos){assert(pos < _size);return _str[pos];}const char& operator[](size_t pos) const{assert(pos < _size);return _str[pos];}

2.3 begin() 和end()

简单用typedef重定义char* 来模拟iterator获取begin（）和end（）

	 typedef char* iterator;iterator begin(){return _str;}iterator end(){return _str + _size;}

2.4capacity（）

获取容量

size_t capacity() const
{return _capacity;
}

2.5 reserve

调整空间

void string::reserve(size_t n)
{if (n > _capacity){char* tmp = new char[n + 1];strcpy(tmp, _str);delete[] _str;_str = tmp;_capacity = n;}
}

2.6push_back

尾插字符

void string::push_back(char ch)
{if (_size = _capacity){reserve(_capacity == 0 ? 4 : _capacity * 2);}_str[_size++] = ch;_str[_size] = '\0';
}

2.7 append

尾插支付串

void  string::append(const char* str){size_t len = strlen(str);
//大于二倍就要多少开多少，低于二倍按二倍开if (_size + len > _capacity){reserve(_size + len > 2 * _capacity ? _size + len : 2 * _capacity);}strcpy(_str + _size, str);_size += len;}

2.8 +=

string& string::operator+=(char ch)
{push_back(ch);return *this;
}string& string::operator+=(const char* str)
{append(str);return *this;
}

2.9insert

在指定位置插入字符或字符串

void string::insert(size_t pos, char ch)
{if (_size == _capacity){reserve(_capacity == 0 ? 4 : _capacity * 2);}assert(pos <= _size);size_t end = _size;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(len==0)
return;if (_size + len > _capacity){reserve(_size + len > 2 * _capacity ? _size + len : 2 * _capacity);}size_t end = _size + len;while (end > pos + len-1){_str[end - len] = _str[end];--end;}for (size_t i = 0; i < len; i++){_str[pos + i] = s[i];}_size += len;
}

2.10 erase

删除指定位置元素

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];}_size -= len;}
}