怎么优化啊+-*/C++

Question

这怎么优化啊

#include <bits/stdc++.h>
using namespace std;
long long x,y,z;
long long f(long long i)
{
    if(i<=x+2)
        return 1;
    return f(i-1)+f(i-x-2)*y;
}
int main() {
    cin>>x>>y>>z;
    cout<<f(1+z);
    return 0;
}

Answer 1

#include <bits/stdc++.h>  
using namespace std;  
  
long long x,y,z;  
map<long long, long long> memo;   
  
long long f(long long i)  
{  
    if(memo.count(i)) return memo[i]; / 
    if(i<=x+2)  
        return 1;  
    long long result = f(i-1) + f(i-x-2)*y;  
    memo[i] = result;   
    return result;  
}  
  
int main() {  
    cin>>x>>y>>z;  
    cout<<f(1+z);  
    return 0;  
}