hdu 2047 递归函数 烤肉串联

#include<iostream>
#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<string>
using namespace std;
	long long save[50];
	long long ans(int n){
		if(save[n])
			return save[n];
			if(n==1)
			save[n]=3;
			else if(n==2)
			save[n]=8;
			else
				save[n]=2*(ans(n-1)+ans(n-2));
			return save[n];
	}
int main(){

	int n;

	while(cin>>n){
		memset(save, 0, sizeof(save));
		cout<<ans(n)<<endl;

	}
return 0;
}