题解 | 牛牛学数列6

#include "iostream"
using namespace std;
int main(){
    int n;
    cin>>n;
    int A[n];
    for(int i = 1;i<=n;i++){
        if(i==1){
            A[i-1]=0;
        }else if(i==2||i==3){
            A[i-1]=1;
        }else{
            A[i-1]=A[i-4]+2*A[i-3]+A[i-2];
        }
    }
    cout<<A[n-1]<<endl;

    return 0;
}