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//使用函数指针 递归加法
typedef  (*fun)(int);

int func1(int n) {
    return 0;
}

int func2(int n) {
    fun f[2] = {func1, func2};
    return n + f[(n != 0)](n - 1);
}

void function1() {
    cout << func2(10) << endl;
}
//----->fun2 end

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//----->fun2 start
//使用静态变量
class test {
    static int N;
    static int sum;
public :
    test() {
        sum += ++N;
    }

    大专栏  递归加法(day1)lass="function">static void reset() {
        N = sum = 0;
    }

    static int getSum() {
        return sum;
    }
};

int test::N = 0;
int test::sum = 0;

void function2() {
    test::reset();
    test *p = new test[10];
    cout << test::getSum() << endl;
    delete[]p;
}
//--->fun2 end

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//----->fun3 start
//使用虚函数的编译多态性

class A {
public:
    virtual int sum(int n) { return 0; };
};

class B : public A {
public:
    int sum(int n) {
        A a;
        B b;
        A *p[2] = {&a, &b};
        return n + p[(n - 1 != 0)]->sum(n - 1);
    }
};

void function3() {
    B b;
    cout << b.sum(10) << endl;
}

//----->fun3 end