HDU 2046 递推

 1 #include<iostream>
 2 #include<cstdio>
 3 #include<algorithm>
 4 #include<cstring>
 5 #include<vector>
 6 #include<cstdlib>
 7 #include<math.h>
 8 using namespace std;
 9 const int inf=0x3f3f3f3;
10 const int maxn=57;
11 long long dp[maxn];
12 long long slove(int n)
13 {
14     dp[1]=1;dp[2]=2;
15     for(int i=3;i<=n;i++)
16     {
17         dp[i]=dp[i-1]+dp[i-2];
18     }
19     return dp[n];
20 }
21 int main()
22 {
23     int n;
24     while(~scanf("%d",&n)){
25         if(n==1){printf("1\n");continue;}
26         if(n==2) {printf("2\n");continue;}
27         long long ans=slove(n);
28         cout<<ans<<endl;
29     }
30 }