#include <bits/stdc++.h> using namespace std; int f(int n){ if(n1||n0) return 1; else return f(n-1)+f(n-2); } int main() { int n; cin>>n; int a=f(n); cout<<a; return 0; }

def f(x):
    if x==1:
        return 1
    elif x==2:
        return 2
    else:
        return f(x-1)+f(x-2)
n=int(input())
print(f(n))

这其实就是一个斐波那契数列，题意即求斐波那契数列的第n项

Python

a: int = 0
b: int = 1

n: int = int(input())

for i in range(n):
    a, b = b, a + b

print(b)

#include<bits/stdc++.h>
using namespace std;
int main()
{
	int a[10086]={0};
	a[1]=1;
	a[2]=2;
	int n;
	cin>>n;
	for(int i=3;i<=n;i++)
	{
		a[i]=a[i-1]+a[i-2];
	}
	cout<<a[n];
}

C++ :

#include <iostream>
using namespace std;
int a[1000]={0};
int main()
{
    int n;
    cin>>n;
    int a=1,b=2,c=3,d=3;
    if(n==1){cout<<a;return 0;}
    if(n==2){cout<<b;return 0;}
    if(n==3){cout<<c;return 0;}
    for(int i=4; i<=n; i++){
        c=b+c;
        a=b;
        b=d;
        d=b+c;
    }
    cout<<c<<endl;
    return 0;
}