实现字符串的作业，挺有意思（别说的你是大神一样。）/*String.h*/#ifndef SSCPP2014_STRING_H#define SSCPP2014_STRING_H #include <iostream> class String {private:char *_buff;int _length, _size; // _size is of the allocated memory public:// constructorsString();explicit String(const char *src);String(const String &src);// destructor~String();// member methodsvoid assign(const char *src);void append(const char &other);void clear();int compare(const String &other) const;const char* c_str() const;bool empty() const;int find(const String &other, int pos = 0) const;int length() const;String substr(const int &pos, const int &count) const;// overload operatorschar& operator[](const int &index);void operator=(const String &other);void operator=(const char *src);String operator+(const String &other) const;bool operator<(const String &other) const;bool operator<=(const String &other) const;bool operator>(const String &other) const;bool operator>=(const String &other) const;bool operator==(const String &other) const;bool operator!=(const String &other) const;// friend methodsfriend std::ostream& operator<<(std::ostream& out, const String &str);// non-meaning static propertystatic char _error_sign; // initial as any char is okay}; #endif/*String.cpp*/ #include "String.h" #include <cstdio> #include <cstring> char String::_error_sign = '\0'; String::String() { _buff = 0; _length = 0; _size = 0; } String::String(const char *src) { _size = std::strlen(src) + 1; _buff = new char[_size]; std::memset(_buff, 0, _size); std::snprintf(_buff, _size, "%s", src); _length = std::strlen(_buff); } String::String(const String &src) { _length = src._length; _size = src._size; _buff = new char[_size]; std::memset(_buff, 0, _size); std::snprintf(_buff, _size, "%s", src._buff); } String::~String() { if (_buff) delete[] _buff; } void String::assign(const char *src) { this->clear(); _size = std::strlen(src) + 1; _buff = new char[_size]; std::memset(_buff, 0, _size); std::snprintf(_buff, _size, "%s", src); _length = std::strlen(_buff); } void String::append(const char &other) { if (this->empty()) { this->assign("A"); _buff[0] = other; } else { if (_length + 1 < _size) { _buff[_length++] = other; } else { _size *= 2; char *new_buff = new char[_size]; std::memset(new_buff, 0, _size); snprintf(new_buff, _size, "%s", _buff); delete[] _buff; _buff = new_buff; _buff[_length++] = other; } } } void String::clear() { _length = _size = 0; if (_buff) { delete[] _buff; _buff = 0; } } int String::compare(const String &other) const { int len = (_length > other._length ? other._length : _length); for (int i = 0; i < len; ++i) { if (_buff[i] < other._buff[i]) return -1; else if (_buff[i] > other._buff[i]) return 1; } if (_length < other._length) return -1; else if (_length > other._length) return 1; else return 0; } const char* String::c_str() const { if (!this->empty()) return _buff; else return ""; } bool String::empty() const { if (_length == 0 ) return true; else return false; } int String::find(const String &other, int pos) const { if (other.empty()) return -3; if (pos >= _length || pos < 0) return -2; if (other._length > _length - pos) return -1; int* overlay_value = new int[other._length + 1]; overlay_value[0] = -1; int i, index = 0, p_index = 0, t_index = pos; for (i = 1; i < other._length; ++i) { index = overlay_value[i - 1]; while (index >= 0 && other._buff[index + 1] != other._buff[i]) index = overlay_value[index]; if (other._buff[index + 1] == other._buff[i]) { overlay_value[i] = index + 1; } else { overlay_value[i] = -1; } } while (p_index < other._length && t_index < _length) { if (_buff[t_index] == other._buff[p_index]) { ++t_index; ++p_index; } else if (p_index == 0) { ++t_index; } else { p_index = overlay_value[p_index - 1] + 1; } } delete[] overlay_value; if (p_index == other._length) { return t_index - p_index; } else { return _length; } } int String::length() const { return _length; } String String::substr(const int &pos, const int &count) const { String ret; if (pos >= _length || pos + count > _length) return ret; ret._buff = new char[count + 1]; ret._size = count + 1; std::memset(ret._buff, 0, ret._size); std::snprintf(ret._buff, count + 1, "%s", _buff + pos); ret._length = std::strlen(ret._buff); return ret; } char& String::operator[](const int &index) { if (index >= 0 && index < _length) return _buff[index]; else return _error_sign; } void String::operator=(const String &other) { this->assign(other.c_str()); } void String::operator=(const char *src) { this->assign(src); } String String::operator+(const String &other) const { String ret; ret._size = _length + other._length + 1; ret._buff = new char[ret._size]; std::snprintf(ret._buff, _length + 1, "%s", _buff); std::snprintf(ret._buff + _length, other._length + 1, "%s", other._buff); ret._length = std::strlen(ret._buff); return ret; } bool String::operator<(const String &other) const { return this->compare(other) == -1 ? true : false; } bool String::operator<=(const String &other) const { return this->compare(other) == 1 ? false : true; } bool String::operator>(const String &other) const { return this->compare(other) == 1 ? true : false; } bool String::operator>=(const String &other) const { return this->compare(other) == -1 ? false : true; } bool String::operator==(const String &other) const { return this->compare(other) == 0 ? true : false; } bool String::operator!=(const String &other) const { return this->compare(other) == 0 ? false : true; } std::ostream& operator<<(std::ostream& out, const String &str) { out << str.c_str(); return out; } 0 0
