//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;
}
