底下两题咋回事？ 一串代码，两题AC

P1044 [NOIP2003 普及组] 栈

P1754 球迷购票问题

打表代码

#include<bits/stdc++.h>
using namespace std;
long long n,f[25]={1,1,2,5,14,42,132,429,1430,4862,16796,58786,208012,742900,2674440,9694845,35357670,129644790,477638700,1767263190,6564120420};//卡特兰数列
int main(){
   cin>>n;
   cout<<f[n];
    return 0;
}