👊E👊题👊要👊取👊模👊

Xylophone

2026-08-15 22:05:15

发布于：广东

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ABC E.
板子。拆贡献。 $a_i^2$ 独立考虑，在剩下 $n-1$ 个数中选 $k-1$ 个数的所有方案都可以贡献一次。然后是式子的乘积贡献，求出每个元素在剩下 $n-1$ 中选出 $k-1$ 个数中的贡献，进行求和，可以快速得出与其他元素的乘积之和。

为什么，最后要，再模一次，我不是，已经，模了，无数次吗，最后再模，是用来，干什么的，防复活？

#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
#define mn(x,y) ((x<y)?(x):(y))
#define mx(x,y) ((x>y)?(x):(y))
#define mid (l+r>>1)
#define int long long
ll n,k,a[200005],b[200005],t[200005],mod=998244353;ll ans,sum,ans2;
ll inv(ll x){
    ll p=mod-2,ans=1;
    while(p){
        if(p&1)ans=ans*x%mod;
        x=x*x%mod;
        p>>=1;
    }
    return ans;
}
inline long long read(){
    long long x=0,f=1,ch=getchar_unlocked();
    for(;!isdigit(ch);ch=getchar_unlocked())if(ch=='-')f=-1;
    for(;isdigit(ch);ch=getchar_unlocked())x=(x<<3)+(x<<1)+(ch^48);
    return x*f;
}
inline void write(long long x){
    x<0?x=-x,putchar_unlocked('-'):0;static short st[19],top(0);
    do st[++top]=x%10,x/=10;while(x);
    while(top)putchar_unlocked(st[top--]|48);
}
signed main(){
    n=read(),k=read();
    for(int i=1;i<=n;++i)a[i]=read();
    t[0]=1;
    for(int i=1;i<=n;++i)t[i]=t[i-1]*i%mod;
    ll s=(((t[n-2]*inv(t[k-2]))%mod)*inv(t[n-k])%mod);
    for(int i=1;i<=n;++i){
        b[i]=s*a[i]%mod;
        sum=(sum+b[i])%mod;
    }
    ll ae=(t[n-1]*inv(t[k-1])%mod)*inv(t[n-k])%mod;
    for(int i=1;i<=n;++i){
        ans=(ans+((((ae*a[i]%mod)%mod)*a[i])%mod))%mod+(((sum+mod-b[i])%mod)*a[i]%mod)%mod;
    }
    write(ans%mod);
    return 0;
}

我真的，求，你，了！AtC，你给我，听，好了，我，背后的，势力，超你。

👊E👊题👊要👊取👊模👊
👊E👊题👊要👊取👊模👊
👊E👊题👊要👊取👊模👊
👊E👊题👊要👊取👊模👊
👊E👊题👊要👊取👊模👊
👊E👊题👊要👊取👊模👊
👊E👊题👊要👊取👊模👊
👊E👊题👊要👊取👊模👊
👊E👊题👊要👊取👊模👊
👊E👊题👊要👊取👊模👊
👊E👊题👊要👊取👊模👊
👊E👊题👊要👊取👊模👊
👊E👊题👊要👊取👊模👊
👊E👊题👊要👊取👊模👊
👊E👊题👊要👊取👊模👊
👊E👊题👊要👊取👊模👊
👊E👊题👊要👊取👊模👊
👊E👊题👊要👊取👊模👊
👊E👊题👊要👊取👊模👊
👊E👊题👊要👊取👊模👊
👊E👊题👊要👊取👊模👊
👊E👊题👊要👊取👊模👊
👊E👊题👊要👊取👊模👊
👊E👊题👊要👊取👊模👊
👊E👊题👊要👊取👊模👊
👊E👊题👊要👊取👊模👊
👊E👊题👊要👊取👊模👊
👊E👊题👊要👊取👊模👊
👊E👊题👊要👊取👊模👊
👊E👊题👊要👊取👊模👊
👊E👊题👊要👊取👊模👊
👊E👊题👊要👊取👊模👊
🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥

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全部评论 6

prediction
[严肃奶龙图] E题要驱魔

2026-08-17 来自浙江
1
- 滚木
  回复
  prediction
  E 题要附魔
  
  2026-08-19 来自浙江
  0
yxdl1
👊E👊题👊要👊取👊模👊

2026-08-16 来自浙江
1
cjdst
可惜了

2026-08-16 来自浙江
1
- Xylophone
  回复
  cjdst
  可惜了
  
  2026-08-16 来自广东
  0
滚木
每次点进 Xyl 的主页都会被闪瞎眼

2026-08-19 来自浙江
0
- Xylophone
  回复
  滚木
  3-2-1，fight！
  
  2026-08-19 来自广东
  0
- Xylophone
  回复
  滚木
  おひさまぱっぱか快晴レース(はいっ)
  ちょこちょこなにげに(そーわっ　So What)
  第一第二第三しーごー
  (だんだんだんだん出番が近づき)
  めんたまギラギラ出走でーす(はいっ！)
  今日もめちゃめちゃはちゃめちゃだっ(ちゃー！)
  がち追い込み(糖質カット)
  コメくいてー(でもやせたーい！)
  あのこは(ワッフォー)そのこは(ベイゴー)
  どいつもこいつも　あらら(リバンドー)
  泣かないで(はいっ)拭くんぢゃねー(おいっ)
  あかちん塗っても(なおらないっ)(はーっ？)
  
  2026-08-19 来自广东
  0
- Xylophone
  回复
  滚木
  きょうの勝利の女神は
  あたしだけにチュゥする
  虹のかなたへゆこう
  風を切って　大地けって
  きみのなかに　光ともす
  (どーきどきどきどきどきどきどきどき)
  
  2026-08-19 来自广东
  0
Asdfre
没绷住

2026-08-16 来自广东
0
Xylophone
@cjdst @MLE_Automaton @Grapher
🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥

2026-08-15 来自广东
0
- MLE_Automaton
  回复
  Xylophone
  阿特我干啥👊🔥
  
  2026-08-16 来自天津
  0

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