牛客网小白月赛1 B，I

 #include <stdio.h>
 #include <math.h>
 #include <string.h>
 #include <stdlib.h>
 #include <iostream>
 #include <sstream>
 #include <algorithm>
 #include <string>
 #include <queue>
 #include <map>
 #include <vector>
 #include <iomanip>
 using namespace std;
 const int maxn = 1e3+;
 const int maxm = 1e4+;
 const int inf = 0x3f3f3f3f;
 const double epx = 1e-;
 typedef long long ll;
 const ll INF = 1e18;
 const double pi = acos(-1.0);
 int main()
 {
     int t,c;
     double a,b;
     cin>>t;
     while(t--)
     {
         cin>>a>>b>>c;
         cout<<setiosflags(ios::fixed)<<setprecision(c)<<(double)pow(a,exp())/b<<endl;//控制输出小数点后位数
     }
 }

I题  卡特兰数 出栈序列有多少种

 #include <stdio.h>
 #include <math.h>
 #include <string.h>
 #include <stdlib.h>
 #include <iostream>
 #include <sstream>
 #include <algorithm>
 #include <string>
 #include <queue>
 #include <map>
 #include <vector>
 #include <iomanip>
 #define mem(a,b) memset(a,b,sizeof(a))
 using namespace std;
 const int maxn = 5e5+;
 const int inf = 0x3f3f3f3f;
 const double epx = 1e-;
 const double pi = acos(-1.0);
 typedef long long ll;
 const ll INF = 1e18;
 const ll mod = ;
 ll n,f[maxn];
 void ff()
 {
     f[]=;
     for(int i=;i<=;i++)
         f[i]=(i*f[i-])%mod;
 }
 ll poww(ll n,ll m)
 {
     ll ans = ;
     while(m > )
     {
         if(m & )ans = (ans * n) % mod;
         m = m >> ;
         n = (n * n) % mod;
     }
     return ans;
 }
 ll cc(ll n,ll m)
 {
     ll ans=f[n];
     ans=(ans*poww(f[m],mod-))%mod;
     ans=(ans*poww(f[n-m],mod-))%mod;
     return ans;
 }
 int main()
 {
     int t,kase=;
     cin>>t;
     ff();
     //cout<<cc(6,3)<<endl;
     while(t--)
     {
         cin>>n;
         int m=n-;
         ll ans1=(cc(*n,n)-cc(*n,n+))%mod;
         ll ans2=(cc(*m,m)-cc(*m,m+))%mod;
         //cout<<ans1<<" "<<ans2<<endl;
         printf("Case #%d: %lld\n",kase++,(ans1-ans2+*mod)%mod);
     }
 }