余数里面的一条公式：(a+b)%3 = (a%3+b%3)%3
1 #include <iostream> 2 using namespace std; 3 int f[1000001]; 4 int main() { 5 int n; 6 f[0] = 7; 7 f[1] = 11; 8 for (int i = 2; i <= 1000000; i++) 9 f[i] = (f[i-1]%3 + f[i-2]%3)%3; 10 while(cin>>n) { 11 if (n < 2) cout<<"no"<<endl; 12 else { 13 if (f[n]== 0) 14 cout<<"yes"<<endl; 15 else 16 cout<<"no"<<endl; 17 } 18 } 19 return 0; 20 }