神奇代码段

1.已经匹配了i个后再加一个字符j变成匹配e[i][j]个

memset(e, 0, sizeof(e));
for(int i = 1; i <= len; i++) {
    int fail = e[i-1][s[i]-'A'];
    e[i-1][s[i]-'A'] = i;
    memcpy(e[i], e[fail], sizeof(e[i]));
}

2.二进制压位背包

//p[x]=-1表明不能组成x，否则能组成 
for(i = 0; i <= tot; i++) {
    p[i] = -1;
    f[i] = 0;
}
p[0] = 0;
f[0] |= 1<<0;
int nn = (tot>>5) + 1;
for(i = 1; i < n; i++) {
    int w = a[i].v;
    int d = w>>5;
    int m = w&31;
    for(j = 0; j < nn; j++) tf[j] = 0;
    for(j = d; j < nn; j++) {
        tf[j] |= f[j-d]<<m;
        if(j+1 < nn && m != 0) tf[j+1] |= f[j-d]>>(32-m);
    }
    for(j = 0; j < nn; j++) if((f[j]|tf[j]) != f[j]) {
        for(k = 0; k < 32; k++) if(!(f[j]&(1<<k)) && (tf[j]&(1<<k))) {
            p[(j<<5)+k] = i;
        }
        f[j] |= tf[j];
    }
}

3.动态访问对象函数

class A
{

};

typedef void (A::*PF)();

class B: public A
{
private:
	int data;
public:
	B(int data):data(data)
	{
	}
	void fun()
	{
		cout<<"Hi, "<<data<<endl;
	}
};

int main() 
{
	PF pf = (PF)(&B::fun);
	B b(3);
	A *pb = &b;
	(pb->*pf)();
	return 0;
}