一个有意思的C++泛型比较技巧文章

来源：互联网发布：淘宝卖家优惠券链接编辑：程序博客网时间：2024/05/21 18:33

//2006-8-23 18:44  李国帅于网络收集除了我感慨的编程者的技能之外，并无其他。里面使用了构造函数，stl，泛型，重载运算符等技巧，虽然都是入门级技巧，不过能把它们灵活运用到一起实现一定目的，已经相当不容易。/**

* Example of Comparator, with rectangles.*/#include <stdio.h>#include <stdlib.h>#include <iostream>#include <vector>using namespace std;/*** A simple rectangle class.*/class Rectangle{public:    //explicit用来防止由构造函数定义的隐式转换。    explicit Rectangle(int len = 0, int wid = 0)        : length(len), width(wid) { }    int getLength() const    {        return length;    }    int getWidth() const    {        return width;    }    void print(ostream & out = cout) const    {        out << "Rectangle " << getLength() << " by " << getWidth();    }private:    int length;    int width;};ostream & operator<< (ostream & out, const Rectangle & rhs){    rhs.print(out);    return out;}/*** Compare object: ordering by length.*/class LessThanByLength{public:    bool operator( ) (const Rectangle & lhs, const Rectangle & rhs) const    {        return lhs.getLength() < rhs.getLength();    }};/*** Compare object: ordering by area.*/class LessThanByArea{public:    bool operator() (const Rectangle & lhs, const Rectangle & rhs) const    {        return lhs.getLength() * lhs.getWidth() < rhs.getLength() * rhs.getWidth();    }};/*** Generic findMax, with a function object.* Precondition: a.size( ) > 0.*/template <class Object, class Comparator>const Object & findMax(const vector<Object> & a, Comparator isLessThan){    int maxIndex = 0;    for (int i = 1; i < a.size(); i++)    if (isLessThan(a[maxIndex], a[i]))        maxIndex = i;    return a[maxIndex];}/*** main: create four rectangles.* find the max, two ways*/int main(){    vector<Rectangle> a;    a.push_back(Rectangle(1, 10));    a.push_back(Rectangle(10, 1));    a.push_back(Rectangle(5, 5));    a.push_back(Rectangle(4, 6));    //这是我添加的//    cout << "push rectangles:" << endl;    for (vector<Rectangle>::iterator it = a.begin(); it != a.end(); it++){        it->print(); cout << endl;    }        cout << "Largest length:\n\t" << findMax(a, LessThanByLength()) << endl;    cout << "Largest area:\n\t" << findMax(a, LessThanByArea()) << endl;    getchar();    return 0;}

阅读全文

0 0