本文主要是介绍Essential C++ 第四章小结，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！
随手画了一个图小结一下：
下面是根据书中的例子写的一些代码：
#include <iostream>
#include <vector>
#include "Triangulate_iterator.h"
using namespace std;static int arr[13] = {1,1,2,3,5,8,13,21,34,55,89,144,233};class Triangulate_iterator;class Triangulate {
public:typedef Triangulate_iterator iterator;/*申明Triangulate_iterator为Triangulate的友元，Triangulate_iterator里的函数都能对Triangulate的私有成员进行访问了*/friend class Triangulate_iterator;Triangulate();Triangulate(int length , int beg_pos);Triangulate(int length);Triangulate(const Triangulate&);Triangulate_iterator begin();Triangulate_iterator end();friend int operator* (const Triangulate_iterator &rhs);int length() const { return _length; }int beg_pos() const { return _beg_pos; }int length() { return _length; }int beg_pos() { return _beg_pos; }bool next(int &x) const;void next_reset() const;static bool is_elem( int );static int get_elem( int pos ) {return _elem[pos];}static void gen_elements( int length );static void gen_elems_to_value( int value );static void display( int length, int beg_pos, ostream &os = cout );static vector<int> _elem;private:string _name;int _length;int _beg_pos;mutable int _next;static const int _max_elems = 1024;};class Triangulate_iterator {
public:friend class Triangulate;Triangulate_iterator(int index) : _index(index-1) {}friend int operator* (const Triangulate_iterator &rhs);bool operator== ( const Triangulate_iterator& ) const;bool operator!= ( const Triangulate_iterator& ) const;int Triangulate_iterator::operator* (const Triangulate_iterator &rhs);Triangulate_iterator& operator++ ();Triangulate_iterator operator++ ( int );private:void check_integrity() const; //检查 _index是否合理int _index;
};class iterator_overflow{};int operator* (const Triangulate_iterator &rhs) {rhs.check_integrity();return Triangulate::_elem[rhs._index];
}
inline bool Triangulate_iterator::operator == ( const Triangulate_iterator& rhs ) const {return this->_index == rhs._index;
}inline bool Triangulate_iterator::operator != ( const Triangulate_iterator& rhs ) const {return (! (*this == rhs ));
}
inline
int Triangulate_iterator::operator* (const Triangulate_iterator &rhs) {rhs.check_integrity();return Triangulate::_elem[_index];
}Triangulate_iterator& Triangulate_iterator::operator++ () {_index++;check_integrity();return *this;
}Triangulate_iterator Triangulate_iterator::operator++ ( int ) {Triangulate_iterator tem = *this;_index++;check_integrity();return tem;
}inline
void Triangulate_iterator::check_integrity() const {if ( _index >= Triangulate::_max_elems)throw iterator_overflow();if(_index >= Triangulate::_elem.size())Triangulate::gen_elements( _index + 1);
}Triangulate_iterator Triangulate::begin() {return Triangulate_iterator(_beg_pos);}Triangulate_iterator Triangulate::end() {return Triangulate_iterator(_beg_pos + _length);
}Triangulate::Triangulate(): _name("Triangulate"),_length(1),_beg_pos(1),_next(0) {}
Triangulate::Triangulate(int l, int b) : _name("Triangulate") {_length = l > 0 ? l : 1;_beg_pos = b > 0 ? b : 1;_next = _beg_pos-1;
}Triangulate::Triangulate(int l) : _name("Triangulate") {_length = l > 0 ? l : 1;_beg_pos = 1;_next = _beg_pos - 1;}Triangulate::Triangulate(const Triangulate &rhs) {_length = rhs._length;_beg_pos = rhs._beg_pos;_next = rhs._next;_name = rhs._name;
}bool Triangulate::next(int &elem) const {if(_next >= _length)return false;elem = _elem[_next];_next++;return true;
}void Triangulate::next_reset() const {_next = _beg_pos - 1;
}vector<int> Triangulate::_elem;int sum( const Triangulate &trian ) {if ( !trian.length())return 0;int sum = 0;int val = 0;trian.next_reset();while ( trian.next( val ))sum += val;return sum;
}bool Triangulate::is_elem( int value ) {if ( !_elem.size() || _elem[_elem.size()-1] < value)gen_elems_to_value(value);vector<int>::iterator found;vector<int>::iterator last = _elem.end();found = find(_elem.begin(), last, value);return found != last;
}void Triangulate::gen_elems_to_value( int value ) {int ix = _elem.size();if ( !ix ) {_elem.push_back(1);ix = 1;}if ( ix == 1) {_elem.push_back(1);ix = 2;}while ( _elem[ix-1] < value && ix < _max_elems) {_elem.push_back(_elem[ix-2] + _elem[ix-1]);ix++;}if( ix == _max_elems )cerr << " value too large " << value << " -- exceeds max size of "<< _max_elems << endl;}void Triangulate::gen_elements( int length ) {if ( length <= 0 || length > _max_elems )return;int ix = _elem.size();if ( length == 1 && ix < length ) {_elem.push_back(1);ix++;}if ( length == 2 && ix < length ) {if( ix == 0) {_elem.push_back(1);++ix;}_elem.push_back(1);++ix;}for (; ix < length; ix++ ) {_elem.push_back(_elem[ix-2] + _elem[ix-1]);}
}int main() {char ch;bool more = true;int i = Triangulate::_elem[0];while( more ) {cout << "Enter your value ";int value;cin >> value;cout << "the value " << (Triangulate::is_elem(value) ? "is " : "is not ")<< "the element of the Triangulate "<< " try more (y/n) " << endl;cin >> ch;if ( ch=='y' || ch=='Y' ) {more = true;} elsemore = false;}return 0;}这篇关于Essential C++ 第四章小结的文章就介绍到这儿，希望我们推荐的文章对编程师们有所帮助！
