递推 + 分支语句

#include <bits/stdc++.h>
using namespace std;
int main(){
	int n,cnt=1,f[1001]={0,1,2};
	cin>>n;
	for (int i=3;i<=n;i++){
		if (i%2==0) f[i]=f[i-1]+f[i/2];
		else f[i]=f[i-1];
	}
	cout<<f[n];
	return 0;
}