【C++】手撕string思路梳理
目录
基本思路
代码实现
1.构建框架：
2.构建函数重载
3.迭代器：
4.遍历string
5.resetve 开空间，insert任意位置插入push_back,append,+=(按顺序依次实现)
6.erase删除，clear清除，resize缩容
7.流插入，流提取
全部代码
本文是对模拟string步骤进行梳理 若要详细讲解请跳转至：【C++】string模拟-CSDN博客
string讲解：【C++】String类-CSDN博客
基本思路
-
构建string类框架
构造函数， 拷贝构造，析构，返回字符串的 C 风格表示，返回字符串长度，返回总容量
-
构建函数重载
operator=,operator[]，> == >= < <= !=
-
迭代器：
begin() && end()
-
遍历string
-
resetve 开空间，insert任意位置插入，push_back,append,+=,交换
-
erase删除，clear清除，resize缩容
-
流插入，流提取
代码实现
1.构建框架：
class string
{
private:
char *_str;
size_t _size;
size_t _capacity;
public:
string(const char *str = "")
: _size(strlen(str))
{
_capacity = _size = 0 ? 3 : _size;
_str = new char[_size + 1];
strcpy(_str, str);
}
// 拷贝
string(const string &s)
: _size(s._size), _capacity(s._capacity)
{
_str = new char[_capacity + 1];
strcpy(_str, s._str);
}
~string()
{
delete[] _str;
_str = nullptr;
_capacity = _size = 0;
}
const char *c_str()
{
return _str;
}
//?
size_t size() const // const?
{
return _size;
}
size_t capacity() const
{
return _capacity;
}
};2.构建函数重载
string &operator=(const string &s)
{
if (this != &s)
{
char *tmp = new char[s._capacity + 1];
strcpy(tmp, s._str);
delete[] _str;
_str = tmp;
_size = s._size;
_capacity = s._capacity;
}
return *this;
}
char &operator[](size_t pos)
{
assert(pos < _size);
return _str[pos];
}
const char &operator[](size_t pos) const
{
assert(pos < _size);
return _str[pos];
}
bool operator<(string &s) const
{
return strcmp(_str, s._str) < 0;
}
bool operator==(string &s) const
{
return strcmp(_str, s._str) == 0;
}
bool operator<=(string &s) const
{
return *this < s || *this == s;
}
bool operator>(string &s) const
{
return !(*this <= s);
}
bool operator>=(string &s) const
{
return !(*this < s);
}
bool operator!=(string &s) const
{
return !(*this == s);
}3.迭代器：
typedef char *iterator;
typedef const char *const_iterator;
iterator begin()
{
return _str;
}
iterator end()
{
return _str + _size;
}4.遍历string
void Print(const string &s)
{
//方法1
for (size_t i = 0; i < s.size(); i++)
{
cout << s[i] << " ";
}
cout << endl;
//方法二：迭代器遍历
const_iterator rit = s.begin();
while (rit != s.end())
{
cout << *rit << " ";
++rit;
}
}5.resetve 开空间，insert任意位置插入push_back,append,+=(按顺序依次实现)
void reserve(size_t n)
{
if (n > _capacity)
{
char *tmp = new char[n + 1];
strcpy(tmp, _str);
delete[] _str;
_str = tmp;
_capacity = n;
}
}
string &insert(size_t pos, char ch)
{
assert(pos <= _size);
// 判断大小
if (_size + 1 > _capacity)
{
reserve(2 * _capacity);
}
size_t end = _size + 1;
while (end > pos)
{
_str[end] = _str[end + 1];
end--;
}
_str[pos] = ch;
++_size;
return *this;
}
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 - len] = _str[end];
--end;
}
strncpy(_str + pos, str, end);
_size += len;
return *this;
}
void push_back(char ch)
{
insert(_size, ch);
}
void append(const char *str)
{
insert(_size, str);
}
string &operator+=(char ch)
{
push_back(ch);
return *this;
}
string &operator+=(const char *str)
{
append(str);
return *this;
}
交换：
void swap(string &s)
{
std::swap(_str, s._str);
std::swap(_capacity, s._capacity);
std::swap(_size, s._size);
}6.erase删除，clear清除，resize缩容
string &erase(size_t pos, size_t len = npos)
{
assert(pos < _size);
if (len == npos || len >= _size)
{
_str[pos] = '\0';
_size = pos;
}
else
{
strcpy(_str + pos, _str + pos + len);
_size -= len;
}
return *this;
}
void resize(size_t n, char ch = '\0')
{
if (n < _size)
{
_size = n;
_str[_size] = '\0';
}
else if (n > _size)
{
if (n > _capacity)
{
reserve(n);
}
size_t i = _size;
while (i < n)
{
_str[i] = ch;
++i;
}
_size = n;
_size = '\0';
}
}
void clear()
{
_str[0] = '\0';
_size = 0;
}7.流插入，流提取
ostream &operator<<(ostream &out, const string &s)
{
for (size_t i = 0; i < s.size(); ++i)
{
out << s[i];
}
return out;
}
istream &operator>>(istream &in, string &s)
{
s.clear();
char ch = in.get();
char buff[128];
size_t i = 0;
while (ch != ' ' && ch != '\n')
{
buff[i++] = ch;
if (i == 127)
{
buff[127] = '\0';
s += buff;
i = 0;
}
ch = in.get();
}
if (i != 0)
{
buff[i] = ch;
buff[i + 1] = '\0';
s += buff;
}
return in;
}全部代码
string.h
#include
#include
using namespace std;
namespace wzf
{
class string
{
private:
char *_str;
size_t _size;
size_t _capacity;
static size_t npos;
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(const char *str = "")
: _size(strlen(str))
{
_capacity = _size = 0 ? 3 : _size;
_str = new char[_size + 1];
strcpy(_str, str);
}
// 拷贝
string(const string &s)
: _size(s._size), _capacity(s._capacity)
{
_str = new char[_capacity + 1];
strcpy(_str, s._str);
}
~string()
{
delete[] _str;
_str = nullptr;
_capacity = _size = 0;
}
string &operator=(const string &s)
{
if (this != &s)
{
char *tmp = new char[s._capacity + 1];
strcpy(tmp, s._str);
delete[] _str;
_str = tmp;
_size = s._size;
_capacity = s._capacity;
}
return *this;
}
char &operator[](size_t pos)
{
assert(pos < _size);
return _str[pos];
}
const char &operator[](size_t pos) const
{
assert(pos < _size);
return _str[pos];
}
bool operator<(string &s) const
{
return strcmp(_str, s._str) < 0;
}
bool operator==(string &s) const
{
return strcmp(_str, s._str) == 0;
}
bool operator<=(string &s) const
{
return *this < s || *this == s;
}
bool operator>(string &s) const
{
return !(*this <= s);
}
bool operator>=(string &s) const
{
return !(*this < s);
}
bool operator!=(string &s) const
{
return !(*this == s);
}
void reserve(size_t n)
{
if (n > _capacity)
{
char *tmp = new char[n + 1];
strcpy(tmp, _str);
delete[] _str;
_str = tmp;
_capacity = n;
}
}
string &insert(size_t pos, char ch)
{
assert(pos <= _size);
// 判断大小
if (_size + 1 > _capacity)
{
reserve(2 * _capacity);
}
size_t end = _size + 1;
while (end > pos)
{
_str[end] = _str[end + 1];
end--;
}
_str[pos] = ch;
++_size;
return *this;
}
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 - len] = _str[end];
--end;
}
strncpy(_str + pos, str, end);
_size += len;
return *this;
}
void push_back(char ch)
{
insert(_size, ch);
}
void append(const char *str)
{
insert(_size, str);
}
string &operator+=(char ch)
{
push_back(ch);
return *this;
}
string &operator+=(const char *str)
{
append(str);
return *this;
}
string &erase(size_t pos, size_t len = npos)
{
assert(pos < _size);
if (len == npos || len >= _size)
{
_str[pos] = '\0';
_size = pos;
}
else
{
strcpy(_str + pos, _str + pos + len);
_size -= len;
}
return *this;
}
void resize(size_t n, char ch = '\0')
{
if (n < _size)
{
_size = n;
_str[_size] = '\0';
}
else if (n > _size)
{
if (n > _capacity)
{
reserve(n);
}
size_t i = _size;
while (i < n)
{
_str[i] = ch;
++i;
}
_size = n;
_size = '\0';
}
}
void clear()
{
_str[0] = '\0';
_size = 0;
}
const char *c_str()
{
return _str;
}
//?
size_t size() const // const?
{
return _size;
}
size_t capacity() const
{
return _capacity;
}
};
size_t string::npos = -1;
ostream &operator<<(ostream &out, const string &s)
{
for (size_t i = 0; i < s.size(); ++i)
{
out << s[i];
}
return out;
}
istream &operator>>(istream &in, string &s)
{
s.clear();
char ch = in.get();
char buff[128];
size_t i = 0;
while (ch != ' ' && ch != '\n')
{
buff[i++] = ch;
if (i == 127)
{
buff[127] = '\0';
s += buff;
i = 0;
}
ch = in.get();
}
if (i != 0)
{
buff[i] = ch;
buff[i + 1] = '\0';
s += buff;
}
return in;
}
void TestString1()
{
string s1("Hello");
cout << s1.c_str() << endl;
string s2 = s1;
string s3(s1);
cout << s3.c_str() << endl;
s1[0]++;
cout << s1.c_str() << endl;
}
void TestString2()
{
string s1("Hello");
cout << s1.c_str() << endl;
string s2("NI");
cout << (s1 > s2) << endl;
cout << (s1 >= s2) << endl;
cout << (s1 == s2) << endl;
cout << (s1 != s2) << endl;
cout << (s1 <= s2) << endl;
}
void TestString3()
{
string s1("Hello");
cout << s1.c_str() << endl;
s1 += '!';
s1 += "2345";
cout << s1.c_str() << endl;
}
void TestString4()
{
string s1("HelloWord");
string s2("HelloWord");
s1.erase(3, 1);
cout << s1.c_str() << endl;
s1.erase(3, 100);
cout << s1.c_str() << endl;
s2.resize(4);
cout << s2.c_str() << endl;
s2.resize(10, 'x');
cout << s2.c_str() << endl;
}
void TestString5()
{
string s1("HelloWord");
cout << s1 << endl;
cin >> s1;
string::iterator it = s1.begin();
while (it != s1.end() - 1)
{
cout << *it << "";
++it;
}
cout << endl;
}
} string.cpp
#include "string.h"
int main()
{
try // char* tmp = new char[s._capacity + 1];是否开辟异常
{
wzf::TestString5();
}
catch (const std::exception &e)
{
std::cerr << e.what() << '\n';
}
return 0;
}