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前言🙌

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string 模拟实现

1、iterator 迭代器相关使用函数实现

        iterator begin(){return _str;}terator end(){return _str + _size;}//针对const对象设计的版本const_iterator begin() const{return _str;}const_iterator end() const{return _str + _size;}

2、构造函数接口实现

		tring(const char* str = ""):_size(strlen(str)), _capacity(_size){_str = new char[_capacity + 1];strcpy(_str, str);}

3、 传统写法——拷贝构造函数接口实现

// 传统写法
//s2(s1)string(const string& s):_str(nullptr),_size(0),_capacity(0){_str = new char[s._capacity + 1];strcpy(_str, s._str);_capacity = s._capacity;_size = s._size;}

4、 现代写法——拷贝构造函数接口实现

// s2(s1)string(const string& s):_str(nullptr), _size(0), _capacity(0){string tmp(s._str);swap(tmp);}

5、析构函数接口实现

		~string(){delete[] _str;_str = nullptr;_size = _capacity = 0;}

6、传统写法—— = 赋值运算符重载函数接口实现

// s2 = s3string& 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;}

7、现代写法—— = 赋值运算符重载函数接口实现

// s2 = s3string& operator=(const string& s){if (this != &s){string tmp(s);//this->swap(tmp);swap(tmp);}return *this;}

8 、极致现代写法—— = 赋值运算符重载函数接口实现

	// s2 = s3string& operator=(string tmp){swap(tmp);return *this;}

9、swap函数接口实现

	void swap(string& s){std::swap(_str, s._str);std::swap(_size, s._size);std::swap(_capacity, s._capacity);}

10、【】下标访问函数接口实现

		char& operator[](size_t pos){assert(pos < _size);return _str[pos];}const char& operator[](size_t pos) const{assert(pos < _size);return _str[pos];}

11、容量、大小数据获取函数接口实现

		size_t capacity() const{return _capacity;}size_t size() const{return _size;}

12、C语言格式函数字符串获取函数接口实现

		const char* c_str() const{return _str;}

13、扩容函数reserve实现接口

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

14、resize函数（实现扩容，改变size，初始化）实现接口

	void resize(size_t n, char ch = '\0'){if (n <= _size){_str[n] = '\0';_size = n;}else{reserve(n);while (_size < n){_str[_size] = ch;++_size;}_str[_size] = '\0';}}

15、find函数接口实现

		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* sub, size_t pos = 0){const char* p = strstr(_str + pos, sub);if (p){return p - _str;}else{return npos;}}

16、substr 取子串函数接口实现

	string substr(size_t pos, size_t len = npos){string s;size_t end = pos + len;if (len == npos || pos + len >= _size) // 有多少取多少{len = _size - pos;end = _size;}s.reserve(len);for (size_t i = pos; i < end; i++){s += _str[i];}return s;}

17、尾插函数接口实现

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

18、append函数（尾插字符串）接口实现

	void append(const char* str){size_t len = strlen(str);if (_size + len > _capacity){reserve(_size + len);}strcpy(_str + _size, str);_size += len;}

19、+= 运算符重载函数实现

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

20、任意位置插入字符/字符串函数接口实现

	// insert(0, 'x')void insert(size_t pos, char ch){assert(pos <= _size);if (_size == _capacity){reserve(_capacity == 0 ? 4 : _capacity * 2);}// 17:17size_t end = _size + 1;while (end > pos){_str[end] = _str[end - 1];--end;}_str[pos] = ch;_size++;}//任意位置插入一个字符串void insert(size_t pos, const char* str){assert(pos <= _size);size_t len = strlen(str);if (_size + len > _capacity){reserve(_size + len);}// 挪动数据int end = _size;while (end >= (int)pos){_str[end + len] = _str[end];--end;}strncpy(_str + pos, str, len);_size += len;}

21、任意位置删除len个字符

	void erase(size_t pos, size_t len = npos){assert(pos < _size);if (len == npos || pos + len >= _size){_str[pos] = '\0';_size = pos;}else{size_t begin = pos + len;while (begin <= _size){_str[begin - len] = _str[begin];++begin;}_size -= len;}}

22、字符串大小比较运算符重载函数实现

		bool operator<(const string& s) const{return strcmp(_str, s._str) < 0;}bool operator==(const string& s) const{return strcmp(_str, s._str) == 0;}bool operator<=(const string& s) const{return *this < s || *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 !(*this == s);}

23、清空函数clear函数接口实现

	void clear(){_str[0] = '\0';_size = 0;}

24、流插入运算符重载函数接口实现

ostream& operator<<(ostream& out, const string& s){/*for (size_t i = 0; i < s.size(); i++){out << s[i];}*/for (auto ch : s)out << ch;return out;}

25、流提取运算符重载函数接口实现

	istream& operator>>(istream& in, string& s){// 17:15继续s.clear();//s.reserve(128);char buff[129];size_t i = 0;char ch;ch = in.get();while (ch != ' ' && ch != '\n'){buff[i++] = ch;if (i == 128){buff[i] = '\0';s += buff;i = 0;}//s += ch;ch = in.get();}if (i != 0){buff[i] = '\0';s += buff;}return in;}

判空函数接口实现

		bool empty()const{return _size == 0;}

总结撒花💞

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