1445D - Divide and Sum - CodeForces Solution

#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
const ll M=998244353;
const int N=1e6;
ll fact[N+2];
ll fast_pow(ll a,ll b){
    if(b==0)
        return 1;
    ll p=fast_pow(a,b/2);
    p=p*p%M;
    if(b&1)
        p=p*a%M;
    return p;
}
void init(){
    fact[0]=1;
    for(int i=1;i<=N;i++){
        fact[i]=fact[i-1]*i%M;
    }
}
ll nCr(ll n,ll r){
    return fact[n]*fast_pow(fact[r],M-2)%M*fast_pow(fact[n-r],M-2)%M;
}
int main(){
    init();
    int n;
    cin>>n;
    ll a[2*n+2];
    for(int i=0;i<2*n;i++){
        cin>>a[i];
    }
    sort(a,a+2*n);
    ll cost=0;
    for(int i=0;i<n;i++)
        cost-=a[i];
    for(int i=n;i<2*n;i++)
        cost+=a[i];
    cost=cost%M;
    cout<<cost*nCr(2*n,n)%M<<endl;
}