string类的模拟实现

目录

构造

迭代器

访问

关系运算符重载

容量

查找插入删除

修改

流插入流提取

---

构造

(传统写法)

（现代写法)：需要引入swap函数改变指针指向

迭代器

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#pragma once
 
#include 
 
namespace sig
{
 
    class string
 
    {
 
        friend ostream& operator<<(ostream& _cout, const sig::string& s)
        {
            for (size_t i = 0; i < s._size; i++)
            {
                _cout << s._str[i];
            }
 
            return _cout;
        }
 
        friend istream& operator>>(istream& _cin, sig::string& s)
        {
            s.clear();
            char buff[129];
            size_t i = 0;
 
            char ch;
            ch = _cin.get();
            while (ch != ' ' && ch != '\n')
            {
                buff[i++] = ch;
                if (i == 128)
                {
                    buff[i] = '\0';
                    s += buff;
                    i = 0;
                }
                ch = _cin.get();
            }
 
            if (i != 0)
            {
                buff[i] = '\0';
                s += buff;
            }
 
            return _cin;
        }
 
    public:
 
        typedef char* iterator;        //可修改迭代器
        typedef char* const_iterator;   //不可修改迭代器
 
 
    public:
 
        string(const char* str = "")
            :_size(strlen(str))
            ,_capacity(_size)
        {
            _str = new char[_capacity + 1];
            strcpy(_str, str);
        }
 
        /*string(const string& s)
        {
            _str = new char[s._capacity + 1];
            strcpy(_str, s._str);
            _size = s._size;
            _capacity = s._capacity;
        }
        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;
        }*/
        //现代写法
        /*void swap(string& s)
        {
            std::swap(_str, s._str);
            std::swap(_size, s._size);
            std::swap(_capacity, s._capacity);
        }*/
 
        string(const string& s)
            :_str(nullptr)
            ,_size(0)
            ,_capacity(0)
        {
            string tmp(s._str);
            swap(tmp);
        }
 
        string& operator=(const string& s)
        {
            if (this != &s)
            {
                string tmp(s);
                swap(tmp);
            }
 
            return *this;
        }
 
        ~string()
        {
            delete[]_str;
            _str = nullptr;
            _size = _capacity = 0;
        }
 
 
 
        //
 
        // iterator
 
        iterator begin()
        {
            return _str;
        }
 
        iterator end()
        {
            return _str + _size;
        }
 
        const_iterator begin()const
        {
            return _str;
        }
 
        const_iterator end()const
        {
            return _str + _size;
        }
 
 
        /
 
        // modify
 
        void push_back(char c)
        {
            if (_size == _capacity)
            {
                reserve(_capacity == 0 ? 4 : 2 * _capacity);
            }
 
            _str[_size] = c;
            _size++;
            _str[_size] = '\0';
        }
 
        string& operator+=(char c)
        {
            push_back(c);
 
            return *this;
        }
 
        void append(const char* str)
        {
            size_t len = strlen(str);
            if (_size + len > _capacity)
            {
                reserve(_size + len);
            }
 
            strcpy(_str + _size, str);
            _size += len;
        }
 
        string& operator+=(const char* str)
        {
            append(str);
 
            return *this;
        }
 
        void clear()
        {
            _str[0] = '\0';
            _size = 0;
        }
 
        void swap(string& s)
        {
            std::swap(_str, s._str);
            std::swap(_size, s._size);
            std::swap(_capacity, s._capacity);
        }
 
        const char* c_str()const
        {
            return _str;
        }
 
 
 
        /
 
        // capacity
 
        size_t size()const
        {
            return _size;
        }
 
        size_t capacity()const
        {
            return _capacity;
        }
 
        bool empty()const
        {
            return _size == 0;
        }
 
        void resize(size_t n, char c = '\0')
        {
            if (n < _size)
            {
                _str[n] = '\0';
                _size = n;
            }
            else
            {
                reserve(n);
                while (_size < n)
                {
                    _str[_size] = c;
                    _size++;
                }
 
                _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;
            }
        }
 
 
 
        /
 
        // access
 
        char& operator[](size_t index)
        {
            assert(index < _size);
 
            return _str[index];
        }
 
        const char& operator[](size_t index)const
        {
            assert(index < _size);
 
            return _str[index];
        }
 
 
 
        /
 
        //relational operators
 
        bool operator<(const string& s)
        {
            return strcmp(_str, s._str) < 0;
        }
 
        bool operator<=(const string& s)
        {
            return _str < s._str || _str == s._str;
        }
 
        bool operator>(const string& s)
        {
            return !(_str <= s._str);
        }
 
        bool operator>=(const string& s)
        {
            return !(_str < s._str);
        }
 
        bool operator==(const string& s)
        {
            return strcmp(_str, s._str) == 0;
        }
 
        bool operator!=(const string& s)
        {
            return _str == s._str;
        }
 
 
 
        // 返回c在string中第一次出现的位置
 
        size_t find(char c, size_t pos = 0) const
        {
            assert(pos < _size);
            for (size_t i = pos; i < _size; i++)
            {
                if (_str[i] == _str[pos])
                {
                    return i;
                }
            }
 
            return npos;
        }
 
        // 返回子串s在string中第一次出现的位置
 
        size_t find(const char* s, size_t pos = 0) const
        {
            const char* p = strstr(_str + pos, s);
            if (p)
            {
                return p - _str;
            }
            else
            {
                return npos;
            }
        }
 
        // 在pos位置上插入字符c/字符串str，并返回该字符的位置
 
        string& insert(size_t pos, char c)
        {
            if (_size == _capacity)
            {
                reserve(_capacity == 0 ? 4 : 2 * _capacity);
            }
 
            size_t end = _size + 1;
            while (end > pos)
            {
                _str[end] = _str[end - 1];
                --end;
            }
            _str[pos] = c;
            _size++;
        }
 
        string& insert(size_t pos, const char* str)
        {
            assert(pos <= _size);
 
            size_t len = strlen(str);
            if (_size + len > _capacity)
            {
                reserve(_size + len);
            }
            int end = _size;
            while (end >= (int)pos)
            {
                _str[end + len] = _str[end];
                --end;
            }
 
            strncpy(_str + pos, str, len);
            _size += len;
        }
 
 
 
        // 删除pos位置上的元素，并返回该元素的下一个位置
 
        string& erase(size_t pos, size_t len)
        {
            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;
            }
        }
 
    private:
 
        char* _str;
 
        size_t _size;
 
        size_t _capacity;
 
        const static size_t npos = -1;
    };
 
}