不容易系列之(3)—— LELE的RPG难题（递推）

 1 #include<iostream>
 2 #include<iomanip>
 3 //#include<bits/stdc++.h>
 4 #include<cstdio>
 5 #include<cmath>
 6 #include<cstring>
 7 #include<algorithm>
 8 #include<sstream>
 9 #define PI  3.14159265358979
10 #define LL long long
11 #define  eps   0.00000001
12 using namespace std;
13 LL f[100];
14 LL solve(LL x)
15 {
16     if(f[x]) return f[x];
17     for(int i=4;i<=x;++i)
18     {
19         f[i]=f[i-1]+2*f[i-2];
20     }
21     return f[x];
22 }
23 int main()
24 {
25       LL T;f[1]=3,f[2]=6,f[3]=6;
26       while(cin>>T)
27       {
28           if(T==1) cout<<3<<endl;
29           else if(T==2) cout<<6<<endl;
30           else if(T==3) cout<<6<<endl;
31           else  cout<<solve(T)<<endl;
32       }
33 }