文章目录
- 底层结构
- ==string类内==
-
- 遍历
-
- [下标加[ ]](#下标加[ ])
- 迭代器(类似指针的版本)和范围for
- 交换函数
- 深拷贝
- 扩容函数
- 在pos前插入字符和字符串
- 在末尾追加一个字符和字符串
- 在pos前删除n个字符
- operator+=接口
- find接口
- 改变容器大小
- 取子串
- 清除容器中的元素
- ==string类外==
- 完整版
底层结构
基本结构,构造函数和析构函数
cpp
namespace mystring
{
class string
{
public:
/*string()
:_str(new char[1])
, _size(0)
, _capacity(0)
{
_str[0] = '\0';
}
string(const char* str)
:_str(new char[strlen(str)+1])
, _size(strlen(str))
, _capacity(strlen(str))
{
strcpy(_str,str);
}*/
//string(const char* str = "\0")
string(const char* str = "")
:_size(strlen(str))
{
_capacity = _size;
_str = new char[_capacity + 1];
strcpy(_str, str);
}
~string()
{
delete[] _str;
_str = nullptr;
_size = _capacity = 0;
}
private:
char* _str;
size_t _size;
size_t _capacity;
public:
static const int npos;
};
const int string::npos = -1;
void StringTest1()
{
string s1("hello world");
}
}
string类内
遍历
下标加[ ]
cpp
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];
}
迭代器(类似指针的版本)和范围for
cpp
typedef char* iterator;
typedef const char* const_iterator;
iterator begin() const
{
return _str;
}
iterator end() const
{
return _str + _size;
}
至于为什么将迭代器实现之后范围for也直接实现了是因为:
范围for
循环的背后机制会自动调用迭代器的begin()
和end()
方法。这是C++标准库提供的一种语法糖,使得遍历容器变得非常方便。
当你定义了一个类,并希望使用范围for
循环来遍历这个类的对象时,你需要在这个类中提供两种特殊的方法:
begin()
方法,返回指向容器中第一个元素的迭代器。end()
方法,返回指向容器中最后一个元素之后的位置的迭代器。
这样,当你使用范围for
循环时,编译器会自动调用这些方法来获取迭代器,然后遍历容器。
交换函数
cpp
//交换函数
void swap(string& s)
{
std::swap(_str,s._str);
std::swap(_size, s._size);
std::swap(_capacity, s._capacity);
}
void swap(string& x, string& y)
{
x.swap(y);
}
深拷贝
cpp
//深拷贝
/*string(const string& s)
{
_str = new char[s._capacity + 1];
strcpy(_str,s._str);
_size = s._size;
_capacity = s._capacity;
}*/
//新写法
string(const string& s)
{
string tmp(s._str);
swap(tmp);
}
//s1=s3
/*string& operator=(const string& s)
{
string ss(s);
swap(ss);
return *this;
}*/
string& operator=(string ss)
{
swap(ss);
return *this;
}
扩容函数
cpp
void reserve(size_t n)
{
if (n > _capacity)
{
char* tmp = new char[n+1];
strcpy(tmp,_str);
delete[] _str;
_str = tmp;
_capacity = n;
}
}
在pos前插入字符和字符串
cpp
//在pos前插入字符
void insert(size_t pos, char ch)
{
assert(pos <= _size);
if (_size == _capacity)
{
reserve(_capacity == 0 ? 4 : 2 * _capacity);
}
/*int end = _size;
while (end >= (int)pos)
{
_str[end + 1] = _str[end];
end--;
}*/
size_t end = _size + 1;
while (end > pos)
{
_str[end] = _str[end-1];
end--;
}
_str[pos] = ch;
++_size;
}
//在pos前插入字符串
void insert(size_t pos, const char* str)
{
assert(pos <= _size);
size_t len = strlen(str);//serlen计算str的长度
if (_size + len > _capacity)
{
reserve(_size + len);
}
size_t end = _size + len;
while (end > pos + len - 1)
{
_str[end] = _str[end - len];
end--;
}
strncpy(_str + pos, str, len);
_size += len;
//_size++;
}
在末尾追加一个字符和字符串
手搓版
cpp
//在末尾追加一个字符
void push_back(char ch)
{
//二倍扩容
if (_size == _capacity)
{
reserve(_capacity==0?4:2*_capacity);
}
_str[_size] = ch;
++_size;
_str[_size] = '\0';
}
//在末尾追加字符串
void append(const char* str)
{
扩容
size_t len = strlen(str);//serlen计算str的长度
if (_size + len > _capacity)
{
reserve(_size + len);
}
strcpy(_str+_size,str);
_size += len;
}
精缩版
因为上面我们已经写了在pos前插入字符和字符串所以我们可以拿来直接用
cpp
//在末尾追加一个字符
void push_back(char ch)
{
insert(_size, ch);
}
//在末尾追加字符串
void append(const char* str)
{
insert(_size, str);
}
在pos前删除n个字符
cpp
//在pos位置删除n个字符
void eraser(size_t pos,size_t len = npos)
{
assert(pos < _size);
if (len == npos || len >= _size - pos)
{
_str[pos] = '\0';
_size = pos;
}
else
{
strcpy(_str + pos, _str + pos + len);
_size -= len;
}
}
operator+=接口
cpp
string& operator+=(char ch)
{
push_back(ch);
return *this;
}
string& operator+=(const char* str)
{
append(str);
return *this;
}
find接口
cpp
//find
size_t find(char ch, size_t pos = 0) const
{
for (size_t i = pos; i < _size; i++)
{
if (_str[i] == ch)
return i;
}
return npos;
}
size_t find(char* str, size_t pos = 0) const
{
//kmp算法,字串匹配,bm算法了解一下
assert(pos < _size);
const char* p = strstr(_str + pos, str);
if (p)
{
return p - _str;
}
else
{
return npos;
}
}
改变容器大小
cpp
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;
}
}
取子串
cpp
//取子串
string substr(size_t pos = 0, size_t len = npos)
{
string sub;
if (len == npos || len >= _size - pos)
{
for (size_t i = pos; i < _size; i++)
{
sub += _str[i];
}
}
else
{
for (size_t i = pos; i < pos + len; i++)
{
sub += _str[i];
}
}
return sub;
}
清除容器中的元素
cpp
void clear()
{
_size = 0;
_str[_size] = '\0';
}
string类外
operator重载
cpp
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 || 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);
}
流插入和流提取+输入流读取一行文本
cpp
ostream& operator<<(ostream& out, const string& s)
{
for (auto ch : s)
{
out << ch;
}
return out;
}
istream& operator>>(istream& in, string& s)
{
s.clear();
char ch;
//in >> ch;
ch = in.get();
while (ch != ' '&& ch != '\n')
{
s += ch;
ch = in.get();
}
return in;
}
istream& getline(istream& in, string& s)
{
s.clear();
char ch;
//in >> ch;
ch = in.get();
char buff[128];
size_t i = 0;
while (ch != '\n')
{
buff[i++] = ch;
if (i == 127)
{
buff[127] = '\0';
s += buff;
i = 0;
}
ch = in.get();
}
if (i > 0)
{
buff[i] = '\0';
s += buff;
}
return in;
}
完整版
.h
cpp
#pragma once
#include <assert.h>
namespace mystring
{
class string
{
public:
/*string()
:_str(new char[1])
, _size(0)
, _capacity(0)
{
_str[0] = '\0';
}
string(const char* str)
:_str(new char[strlen(str)+1])
, _size(strlen(str))
, _capacity(strlen(str))
{
strcpy(_str,str);
}*/
const char* c_str() const
{
return _str;
}
//string(const char* str = "\0")
string(const char* str = "")
:_size(strlen(str))
{
_capacity = _size;
_str = new char[_capacity + 1];
strcpy(_str,str);
}
//深拷贝
/*string(const string& s)
{
_str = new char[s._capacity + 1];
strcpy(_str,s._str);
_size = s._size;
_capacity = s._capacity;
}*/
//新写法
string(const string& s)
{
string tmp(s._str);
swap(tmp);
}
//s1=s3
/*string& operator=(const string& s)
{
string ss(s);
swap(ss);
return *this;
}*/
string& operator=(string ss)
{
swap(ss);
return *this;
}
//析构函数
~string()
{
delete[] _str;
_str = nullptr;
_size = _capacity = 0;
}
//扩容函数
void reserve(size_t n)
{
if (n > _capacity)
{
char* tmp = new char[n+1];
strcpy(tmp,_str);
delete[] _str;
_str = tmp;
_capacity = n;
}
}
//在末尾追加一个字符
void push_back(char ch)
{
//二倍扩容
/*if (_size == _capacity)
{
reserve(_capacity==0?4:2*_capacity);
}
_str[_size] = ch;
++_size;
_str[_size] = '\0';*/
insert(_size, ch);
}
//在末尾追加字符串
void append(const char* str)
{
//扩容
//size_t len = strlen(str);//serlen计算str的长度
//if (_size + len > _capacity)
//{
// reserve(_size + len);
//}
//strcpy(_str+_size,str);
//_size += len;
insert(_size, str);
}
string& operator+=(char ch)
{
push_back(ch);
return *this;
}
string& operator+=(const char* str)
{
append(str);
return *this;
}
//在pos前插入字符
void insert(size_t pos, char ch)
{
assert(pos <= _size);
if (_size == _capacity)
{
reserve(_capacity == 0 ? 4 : 2 * _capacity);
}
/*int end = _size;
while (end >= (int)pos)
{
_str[end + 1] = _str[end];
end--;
}*/
size_t end = _size + 1;
while (end > pos)
{
_str[end] = _str[end-1];
end--;
}
_str[pos] = ch;
++_size;
}
//在pos前插入字符串
void insert(size_t pos, const char* str)
{
assert(pos <= _size);
size_t len = strlen(str);//serlen计算str的长度
if (_size + len > _capacity)
{
reserve(_size + len);
}
size_t end = _size + len;
while (end > pos + len - 1)
{
_str[end] = _str[end - len];
end--;
}
strncpy(_str + pos, str, len);
_size += len;
//_size++;
}
//在pos位置删除n个字符
void eraser(size_t pos,size_t len = npos)
{
assert(pos < _size);
if (len == npos || len >= _size - pos)
{
_str[pos] = '\0';
_size = pos;
}
else
{
strcpy(_str + pos, _str + pos + len);
_size -= len;
}
}
//交换函数
void swap(string& s)
{
std::swap(_str,s._str);
std::swap(_size, s._size);
std::swap(_capacity, s._capacity);
}
//find
size_t find(char ch,size_t pos = 0) const
{
for (size_t i = pos; i < _size; i++)
{
if (_str[i] == ch)
return i;
}
return npos;
}
size_t find(char* str, size_t pos = 0) const
{
//kmp算法,字串匹配,bm算法了解一下
assert(pos < _size);
const char* p = strstr(_str + pos, str);
if (p)
{
return p - _str;
}
else
{
return npos;
}
}
//取子串
string substr(size_t pos = 0, size_t len = npos)
{
string sub;
if (len == npos || len >= _size - pos)
{
for (size_t i = pos; i < _size; i++)
{
sub += _str[i];
}
}
else
{
for (size_t i = pos; i < pos + len; i++)
{
sub += _str[i];
}
}
return sub;
}
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;
}
}
//下标遍历
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];
}
//迭代器(范围for)遍历
typedef char* iterator;
typedef const char* const_iterator;
iterator begin() const
{
return _str;
}
iterator end() const
{
return _str + _size;
}
void clear()
{
_size = 0;
_str[_size] = '\0';
}
private:
char* _str;
size_t _size;
size_t _capacity;
public:
static const int npos;
};
const int string::npos = -1;
void swap(string& x, string& y)
{
x.swap(y);
}
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 || 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();
char ch;
//in >> ch;
ch = in.get();
while (ch != ' '&& ch != '\n')
{
s += ch;
ch = in.get();
}
return in;
}
istream& getline(istream& in, string& s)
{
s.clear();
char ch;
//in >> ch;
ch = in.get();
char buff[128];
size_t i = 0;
while (ch != '\n')
{
buff[i++] = ch;
if (i == 127)
{
buff[127] = '\0';
s += buff;
i = 0;
}
ch = in.get();
}
if (i > 0)
{
buff[i] = '\0';
s += buff;
}
return in;
}
void StringTest1()
{
string s1("hello world");
string s2;
cout << s1.c_str() << endl;
cout << s2.c_str() << endl;
/*for (size_t i = 0; i < s1.size(); i++)
{
s1[i]--;
}
cout << endl;*/
for (size_t i = 0; i < s1.size(); i++)
{
cout << s1[i] << " ";
}
cout << endl;
const string s3("xxxxxxx");
for (size_t i = 0; i < s3.size(); i++)
{
cout << s3[i] << " ";
}
cout << endl;
}
void StringTest2()
{
string s3("hello world");
string::iterator it3 = s3.begin();
while (it3 != s3.end())
{
cout << *it3 << " ";
++it3;
}
cout << endl;
const string s4("xxxxxxxx");
string::const_iterator it4 = s4.begin();
while (it4 != s4.end())
{
cout << *it4 << " ";
++it4;
}
cout << endl;
for (auto ch : s3)
{
cout << ch << " ";
}
}
void StringTest3()
{
string s1("hello world!");
cout << s1.c_str() << endl;
s1 += 'x';
cout << s1.c_str() << endl;
s1 += "abcdefg";
cout << s1.c_str() << endl;
string s2("hello world");
s2.insert(0, 'x');
cout << s2.c_str() << endl;
}
void StringTest4()
{
string s1("hello world");
cout << s1.c_str() << endl;
/*s1.eraser(6, 3);
cout << s1.c_str() << endl;*/
string s2(s1);
cout << s2.c_str() << endl;
s2.resize(20, '*');
cout << s2.c_str() << endl;
}
void StringTest5()
{
string s1("hello world");
string s2("test");
cout << s1.c_str() << endl;
s1.insert(6,"xxx");
cout << s1.c_str() << endl;
cout << s2.c_str() << endl;
s1.swap(s2);
cout << s1.c_str() << endl;
cout << s2.c_str() << endl;
}
void StringTest6()
{
string url("https://www.baidu.com/");
size_t goal = url.find("baidu");
cout << goal << endl;
}
void StringTest7()
{
string s1("asdfghjk");
string s2("asdfghjk");
cout << (s1 == s2) << endl;
cout << (s1 == "asdfghjk") << endl;
cout << ("asdfghjk" == s2) << endl;
cout << s1 << endl;
cout << s2 << endl;
cin >> s1 >> s2;
cout << s1 << endl;
cout << s2 << endl;
getline(cin,s1);
cout << s1 << endl;
cout << s2 << endl;
}
void StringTest8()
{
string s1("hello world");
string s2;
cout << s1 << endl;
cout << s2 << endl;
s2 = s1;
cout << s1 << endl;
cout << s2 << endl;
}
}