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QOJ

IDProblemSubmitterResultTimeMemoryLanguageFile sizeSubmit timeJudge time
#136671#242. RMQ Similar SequenceVengeful_Spirit#100 ✓493ms98128kbC++201.4kb2023-08-09 09:55:182023-08-09 09:55:22

Judging History

This is the latest submission verdict.

  • [2023-08-10 23:21:45]
  • System Update: QOJ starts to keep a history of the judgings of all the submissions.
  • [2023-08-09 09:55:22]
  • Judged
  • Verdict: 100
  • Time: 493ms
  • Memory: 98128kb
  • [2023-08-09 09:55:18]
  • Submitted

answer

#include<bits/stdc++.h>
using namespace std;
const int N=2e6+5;
const int mo=1e9+7;
int sz[N],c[N][2],a[N],st[N];
int fa[N];
int fac[N],inv[N];
int qpow(int a,int b){
  int res=1;
  for(;b;b>>=1,a=1ll*a*a%mo){
    if(b&1)res=1ll*res*a%mo;
  }
  return res;
}
void init(){
  fac[0]=1;
  for(int i=1;i<N;i++){
    fac[i]=1ll*fac[i-1]*i%mo;
  }
  for(int i=0;i<N;i++){
    inv[i]=qpow(fac[i],mo-2);
  }
}
int C(int n,int m){
  return 1ll*fac[n]*inv[n-m]%mo*inv[m]%mo;
}
int solve(int x){
  if(!x)return 1;
  sz[x]=1;
  int res=1ll*solve(c[x][0])*solve(c[x][1])%mo;
  sz[x]+=sz[c[x][0]];
  sz[x]+=sz[c[x][1]];
  res=1ll*res*C(sz[x]-1,sz[c[x][0]])%mo;
 // cout<<"C "<<sz[x]-1<<" "<<sz[c[x][0]]<<endl;
 // cout<<x<<" "<<sz[x]<<" "<<res<<endl;
  return res;
}
int tp;
int main(){
  int T;
  scanf("%d",&T);
  init();
  while(T--){
    int n;
    scanf("%d",&n);
    for(int i=1;i<=n;i++)st[i]=fa[i]=c[i][0]=c[i][1]=0;
    tp=0;
    for(int i=1;i<=n;i++){
      scanf("%d",&a[i]);
      st[tp+1]=0;
      while(tp&&(a[st[tp]]<a[i]))--tp;
      c[c[st[tp]][1]=i][0]=st[tp+1];
      st[++tp]=i;
    }
    for(int i=1;i<=n;i++){
      fa[c[i][0]]=i;
      fa[c[i][1]]=i;
    }
    int rt=0;
    for(int i=1;i<=n;i++){
      if(!fa[i])rt=i;
    }
    int ans=solve(rt);
    ans=1ll*ans*inv[n]%mo;
    ans=1ll*ans*n%mo*qpow(2,mo-2)%mo;
    printf("%d\n",ans);
  }
}

Details

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Test #1:

score: 100
Accepted
time: 493ms
memory: 98128kb

input:

11119
1
1
2
1 2
3
1 1 3
4
3 1 1 2
5
5 5 2 4 2
6
2 6 4 4 3 3
7
3 1 1 3 5 5 4
8
4 8 4 7 1 1 7 6
9
9 3 6 3 7 6 1 7 6
10
5 1 10 2 5 1 7 7 4 1
10
4 5 4 5 10 1 5 1 2 5
10
1 2 3 6 2 9 9 7 6 2
10
2 8 3 5 2 4 10 4 8 4
10
2 9 10 3 1 1 2 10 7 7
10
5 7 7 8 10 6 4 3 10 6
10
1 8 9 3 2 4 2 5 5 9
10
4 7 9 2 5 10 10...

output:

500000004
500000004
250000002
83333334
41666667
520833337
760416672
760416672
190104168
1984127
952083340
650694449
253472224
625744052
301388891
625744052
952083340
63368056
387723217
462574408
500992067
835648154
877232149
476041670
31684028
354456021
877232149
916832017
559076007
650694449
126736...

result:

ok 11119 lines