题意:
题解:
就是分子
AC代码
/* Author:zzugzx Lang:C++ Blog:blog.csdn.net/qq_43756519 */ #include<bits/stdc++.h> using namespace std; #define fi first #define se second #define pb push_back #define mp make_pair #define all(x) (x).begin(),(x).end() #define endl '\n' #define SZ(x) (int)x.size() typedef long long ll; typedef pair<int, int> pii; typedef pair<ll, ll> pll; typedef pair<double,double> pdd; const int mod=1e9+7; //const int mod=998244353; const double eps = 1e-10; const double pi=acos(-1.0); const int maxn=1e6+10; const ll inf=0x3f3f3f3f; const int dir[8][2]={{0,1},{1,0},{0,-1},{-1,0},{1,1},{1,-1},{-1,1},{-1,-1}}; ll dp[50][200]; int main() { ios::sync_with_stdio(false); cin.tie(0);cout.tie(0); //freopen("in.txt","r",stdin); //freopen("out.txt","w",stdout); ll n; cin>>n; ll N=4*n; dp[0][0]=1; for(int i=1;i<=n;i++) for(int j=1;j<=4;j++) for(int k=N;k>=j;k--) dp[i][k]+=dp[i-1][k-j]; ll ans=0; for(int i=3*n;i<=N;i++)ans+=dp[n][i]; N=1ll<<(2*n); ll x=__gcd(ans,N); cout<<ans/x<<'/'<<N/x<<endl; return 0; }