Submission #40988802

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Source Code Expand

#include<atcoder/all>

#include<bits/stdc++.h>
#define rep(i,a,b) for(int i=(a);i<=(b);i++)
#define per(i,a,b) for(int i=(a);i>=(b);i--)
#define op(x) ((x&1)?x+1:x-1)
#define odd(x) (x&1)
#define even(x) (!odd(x))
#define lc(x) (x<<1)
#define rc(x) (lc(x)|1)
#define lowbit(x) (x&-x)
#define mp(x,y) make_pair(x,y)
typedef long long ll;
typedef unsigned long long ull;
typedef double db;
using namespace std;
using namespace atcoder;
const int MAXN=(1<<20)+10,mod=998244353,INF=1e9;
ll mypow(ll a,ll n){
    if(!n)return 1;
    ll tmp=mypow(a,n/2);tmp=tmp*tmp%mod;
    if(n&1)tmp=tmp*a%mod;return tmp;
}
ll myinv(ll a){return mypow(a,mod-2);}
void add(ll& x,ll v){x=(x+v)%mod;}
void sub(ll& x,ll v){x=(x+mod-v)%mod;}


namespace INV{
    vector<ll> solve(vector<ll> A,int N){
        if(N==1){
            vector<ll>ret(1);
            ret[0]=myinv(A[0]);
            return ret;
        }
        vector<ll> F0=solve(A,(N+1)>>1);
        A.resize(N,0);
        A=convolution(A,F0);A.resize(N,0);
        A=convolution(A,F0);A.resize(N,0);
        F0.resize(N,0);
        rep(i,0,N-1)F0[i]=F0[i]*2%mod,sub(F0[i],A[i]);
        return F0;
    }  
};
vector<ll> inv(vector<ll> p,int N){return INV::solve(p,N+1);}
//

namespace CFM{
    const ll MAXN=1e6+10,div2=(mod+1)/2;

    ll n,m,LIM=1e6;

    ll F[MAXN],G[MAXN],ans;

    ll fact[MAXN],rfact[MAXN];

    ll C(ll n,ll m){
        if(m<0 || n<m)return 0;
        return fact[n]*rfact[m]%mod*rfact[n-m]%mod;
    }

    void pre_solve1(){
        vector<ll> f(n+1,0),g(n+1,0);
        rep(i,0,n)f[i] = C(m-n+2*i,i)%mod;
        rep(i,1,n)g[i] = C(2*i,i)%mod;
        g[0]=1;
        vector<ll> pF=convolution(f,inv(g,n));
        rep(i,0,n)F[i]=pF[i]*(m-n+i)%mod;
    }
    void pre_solve2(){
        vector<ll> f(n+1,0),g(n+1,0);
        f[0]=(mod-1);
        rep(i,1,n)g[i] = C(2*i,i);
        g[0]=1;
        vector<ll> pF=convolution(f,inv(g,n));
        rep(i,1,n)G[i] = pF[i];
    }
    void solve1(){
        vector<ll>pF(n+1,0),pG(n+1,0);
        
        rep(i,0,n)pF[i] = F[i],pG[i] = C(2*i,i);

        pF=convolution(pF,pG);
        add(ans,pF[n]);
    }
    void solve2(){
        vector<ll>pF(n+1,0),pG(n+1,0),pH(n+1,0);
        rep(i,0,n)pF[i] = C(2*i,i),pH[i] = C(2*i+m-n,i);

        pF=convolution(pF,pH);pF.resize(n+1);

        rep(i,1,n)pG[i] = G[i]*div2%mod*(2*i+1)%mod;

        pF=convolution(pF,pG);
        add(ans,pF[n]);
    }
    void solve(){
        
        fact[0]=1;
        rep(i,1,LIM)fact[i]=fact[i-1]*i%mod;
        rfact[LIM]=myinv(fact[LIM]);
        per(i,LIM-1,0)rfact[i]=rfact[i+1]*(i+1)%mod;

        cin>>n>>m;
        if(n>m)swap(n,m);
        if(n==0 || m==0){
            cout<<n+m<<endl;
            exit(0);
        }

        pre_solve1();
        pre_solve2();

        solve1();   
        solve2();
        cout<<ans*myinv(C(n+m,n))%mod<<endl;
        
    }

};

int main(){
    CFM::solve();

    return 0;
}

Submission Info

Compile Error

./Main.cpp: In function ‘ll mypow(ll, ll)’:
./Main.cpp:22:5: warning: this ‘if’ clause does not guard... [-Wmisleading-indentation]
   22 |     if(n&1)tmp=tmp*a%mod;return tmp;
      |     ^~
./Main.cpp:22:26: note: ...this statement, but the latter is misleadingly indented as if it were guarded by the ‘if’
   22 |     if(n&1)tmp=tmp*a%mod;return tmp;
      |                          ^~~~~~

Judge Result