string类的模拟实现
private:
char* _str;
size_t _size;
size_t _capacity;
static const size_t npos;
1. 构造函数
String(const char* str = "")
{
_size = strlen(str);
_str = new char[_size + 1];
_capacity = _size;
strcpy(_str, str);
}
String(const String& s)
:_str(nullptr)
, _size(0)
, _capacity(0)
{
String tmp(s._str);
Swap(tmp);
}
void Swap(String& str)
{
swap(_str, str._str);
swap(_size, str._size);
swap(_capacity, str._capacity);
}
2. 析构函数
~String()
{
if (_str)
{
delete[] _str;
_str = nullptr;
}
}
3. 赋值运算符重载函数
String& operator=(const String &s)
{
if (this != &s)
{
String tmp(s);
this->Swap(tmp);
}
return *this;
}
char& operator[](size_t index)
{
assert(index < _size);
return _str[index];
}
const char& operator[](size_t index)const
{
assert(index < _size);
return _str[index];
}
String& operator+=(const char* str)
{
append(str);
return *this;
}
String& operator+=(const String& str)
{
this->append(str._str);
return *this;
}
String& operator+=(char c)
{
push_back(c);
return *this;
}
4. 字符串的长度、容量,判空、清空
size_t size()const
{
return _size;
}
size_t capacity()const
{
return _capacity;
}
bool empty()const
{
return _size == 0;
}
void clear()
{
_size = 0;
_str[_size] = '\0';
}
const char* c_str()const
{
return _str;
}
5. 迭代器(iterator)
iterator begin()
{
return _str;
}
iterator end()
{
return _str + _size;
}
const iterator begin()const
{
return _str;
}
const iterator end()const
{
return _str + _size;
}
6. 修改字符串长度、容量
void resize(size_t n, char c = '\0')
{
if (n > _capacity)
{
reserve(n);
}
if (n > _size)
{
memset(_str + _size, c, (n - _size) * sizeof(char));
}
_size = n;
_str[_size] = '\0';
}
void reserve(size_t n)
{
if (n > _capacity)
{
char* tmp = new char[n + 1];
strcpy(tmp, _str);
delete[] _str;
_str = tmp;
_capacity = n;
}
}
7. 字符串尾插、追加、插入、删除
void push_back(char c)
{
if (_size == _capacity)
{
size_t newC = _capacity == 0 ? 15 : 2 * _capacity;
reserve(newC);
}
_str[_size++] = c;
_str[_size] = '\0';
}
void append(const char* str)
{
int len = strlen(str);
if (_size + len > _capacity)
{
reserve(_size + len);
}
memcpy(_str + _size, str, sizeof(char)*len);
_size += len;
_str[_size] = '\0';
}
String& insert(size_t pos, char c)
{
assert(pos <= _size);
if (_size == _capacity)
{
size_t newC = _capacity = 0 ? 15 : 2 * _capacity;
reserve(newC);
}
size_t end = _size + 1;
while (end > pos)
{
_str[end] = _str[end - 1];
--end;
}
_str[pos] = c;
++_size;
return *this;
}
String& insert(size_t pos, const char* str)
{
assert(pos <= _size);
int 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, sizeof(char)*len);
_size += len;
return *this;
}
String& erase(size_t pos, size_t len)
{
assert(pos < _size);
if (pos + len >= _size)
{
_size = pos;
_str[_size] = '\0';
}
else {
size_t start = pos + len;
for (; start <= _size; ++start)
{
_str[pos++] = _str[start];
}
_size -= len;
}
return *this;
}
8. 字符串的比较
bool operator<(const String& s)
{
int ret = strcmp(_str, s._str);
if (ret < 0)
return true;
return false;
}
bool operator<=(const String& s)
{
return !(*this > s);
}
bool operator>(const String& s)
{
int ret = strcmp(_str, s._str);
if (ret > 0)
return true;
return false;
}
bool operator>=(const String& s)
{
return !(*this < s);
}
bool operator==(const String& s)
{
int ret = strcmp(_str, s._str);
if (ret == 0)
return true;
return false;
}
bool operator!=(const String& s)
{
return !(*this == s);
}
9. 字符串查找
size_t find(char c, size_t pos = 0) const
{
for (size_t i = 0; i < _size; ++i)
{
if (_str[i] == c)
{
return i;
}
return npos;
}
}
size_t find(const char* s, size_t pos = 0) const
{
char* ptr = strstr(_str,s);
if (ptr)
{
return ptr - _str;
}
return npos;
}