函数递归题解

#include<iostream>
#include<string>
using namespace std;
int n;
//void fish(string& a,string& b,string& c){a=b,b=c,c=b+a;}
void fish(string& a,string& b,string& c){
    if(c.size()<n){
        a=b,b=c,c=b+a;
        fish(a,b,c);
    }
    return ;
}
string a="4567",b="123",c="1234567";
int main(){
    //int n;
    cin>>n;
    //while(c.size()<n)fish(a,b,c);
    fish(a,b,c);
    cout<<c[n-1];
    return 0;
}