嗖嗖嗖

 1 #include<cstring>
 2 #include<cstdlib>
 3 #include<cstdio>
 4 //#include<assert.h>
 5 //#include<time.h>
 6 #include<math.h>
 7 //#include<queue>
 8 #include<algorithm>
 9 //#include<iostream>
10 using namespace std;
11 
12 int n;
13 #define maxn 100011
14 int a[maxn],fail[maxn],indo[maxn];
15 int ll[maxn],rr[maxn];
16 int da[maxn],xiao[maxn],pos[maxn];
17 void pre()
18 {
19     for (int i=0;i<=n;i++) rr[i]=i+1;
20     for (int i=1;i<=n+1;i++) ll[i]=i-1;
21     for (int i=n;i>=1;i--)
22     {
23         da[i]=pos[rr[a[i]]];
24         xiao[i]=pos[ll[a[i]]];
25         rr[ll[a[i]]]=rr[a[i]];
26         ll[rr[a[i]]]=ll[a[i]];
27         cout<<da[i]<<‘ ‘<<xiao[i]<<endl;
28     }
29 }
30 void makefail(int x)
31 {
32     if (x<3) fail[x]=1;
33     else
34     {
35         int j=fail[x-1];
36         while (j>1 && !((!da[j] || a[x-1-(j-da[j])]>a[x-1]) && (!xiao[j] || a[x-1-(j-xiao[j])]<a[x-1]))) j=fail[j];
37         fail[x]=((!da[j] || a[x-1-(j-da[j])]>a[x-1]) && (!xiao[j] || a[x-1-(j-xiao[j])]<a[x-1]))?j+1:1;
38         indo[fail[x]]++;
39 //        cout<<x<<‘ ‘<<fail[x]<<endl;
40     }
41 }
42 int que[maxn],head,tail,size[maxn];
43 #define LL long long
44 LL work()
45 {
46     head=tail=0;
47     for (int i=2;i<=n+1;i++)
48     {
49         if (!indo[i]) que[tail++]=i;
50         size[i]=1;
51     }
52     LL ans=0;
53     while (head!=tail)
54     {
55         const int now=que[head++];
56         if (now==1) continue;
57         indo[fail[now]]--;
58         size[fail[now]]+=size[now];
59         if (!indo[fail[now]]) que[tail++]=fail[now];
60         ans=max(ans,(now-1)*1ll*size[now]);
61     }
62     return ans;
63 }
64 int main()
65 {
66 //    freopen("sub.in","r",stdin);
67 //    freopen("sub.out","w",stdout);
68     scanf("%d",&n);
69     for (int i=1;i<=n;i++) scanf("%d",&a[i]),pos[a[i]]=i;
70     pre();
71     fail[1]=1;
72     for (int i=1;i<=n;i++) makefail(i+1);
73     printf("%lld\n",work());
74     return 0;
75 }