策略模式

策略模式（Strategy）:定义了算法家族，分别封装起来，让它们之间可以互相替换，此模式让算法的变化，不会影响到使用算法的客户。[DP]

以下为策略模式的实现代码。

 1 #include<iostream>
 2 using namespace std;
 3 
 4 class Strategy{
 5 public:
 6     Strategy(void){}
 7     virtual ~Strategy(void){}
 8 
 9     virtual void AlgorithmInterface()=0;
10 };
11 
12 class ConcreteStrategyA:public Strategy{
13 public:
14     void AlgorithmInterface(){
15         cout<<"ConcreteStrategyA:AlgorithmInterface()"<<endl;
16     }
17 };
18 
19 class ConcreteStrategyB:public Strategy{
20 public:
21     void AlgorithmInterface(){
22         cout<<"ConcreteStrategyB:AlgorithmInterface()"<<endl;
23     }
24 };
25 
26 class Context{
27 private:
28     Strategy* strategy;
29 public:
30     Context(Strategy* s):strategy(s){}
31     void setStrategy(Strategy* s){
32         strategy=s;
33     }
34     void otherOperators(){
35         cout<<"other operators"<<endl;
36     }
37 
38     void execute(){
39         if(strategy)
40             strategy->AlgorithmInterface();
41         otherOperators();
42     }
43 };
44 
45 int main()
46 {
47     ConcreteStrategyA strategyA;
48     ConcreteStrategyB strategyB;
49     Context context(&strategyA);
50     context.execute();
51     context.setStrategy(&strategyB);
52     context.execute();
53 
54          return 0;
55 }