hdu 2046递推

递推公式   F[N]=F[N-1]+F[N-2];

AC代码：

#include<cstdio>
const int maxn=55;
long long ans[maxn];
void solve(){
    ans[1]=1;
    ans[2]=2;
    for(int i=3;i<=50;++i){
        ans[i]=ans[i-1]+ans[i-2];
    }
}
int main(){
    solve();
    int n;
    while(scanf("%d",&n)!=EOF){
        printf("%lld\n",ans[n]);
    }
    return 0;
}