美丽的序列

 1 #include<iostream>
 2 #include<cstdio>
 3 #include<cstdlib>
 4 #include<cmath>
 5 #include<algorithm>
 6 #include<cstring>
 7 using namespace std;
 8 typedef long long LL;
 9 const LL inf=1e12;
10 inline LL read(){
11     LL x=0,f=1;char ch=getchar();
12     while(ch<‘0‘||ch>‘9‘){if(ch==‘-‘)f=-1;ch=getchar();}
13     while(ch>=‘0‘&&ch<=‘9‘){x=x*10+ch-‘0‘;ch=getchar();}
14     return x*f;
15 }
16 LL N,a[2000001];
17 LL last[2000001],next[2000001];
18 LL q1[2000001],pos1[2000001],h1,t1;
19 LL q2[2000001],pos2[2000001],h2,t2;
20 inline void calc1();
21 inline void calc2();
22 LL maxx;
23 int main(){
24     N=read();
25     for(int i=1;i<=N;i++) a[i]=read();
26     calc1();
27     calc2();
28     for(int i=1;i<=N;i++){
29         LL tmp=(next[i]-last[i]-1)*a[i];
30         if(maxx<tmp) maxx=tmp;
31     }
32     cout<<maxx;
33     return 0;
34 }
35 inline void calc1(){
36     q1[1]=a[1];pos1[1]=1; h1=t1=1;
37     int now=2;
38     while(now<=N){
39         while(t1>=h1&&q1[t1]>=a[now]){
40             t1--;
41         }
42         t1++;
43         q1[t1]=a[now];
44         pos1[t1]=now;
45         last[now]=pos1[t1-1];
46         now++;
47     }
48 }
49 inline void calc2(){
50     q2[N]=a[N]; pos2[N]=N; h2=t2=N,next[N]=N+1;
51     int now=N-1;
52     while(now>=1){
53         while(t2<=h2&&q2[t2]>=a[now]){
54             t2++;
55         }
56         t2--;
57         q2[t2]=a[now];
58         pos2[t2]=now;
59         next[now]=pos2[t2+1];
60         if(next[now]==0) next[now]=N+1;
61         now--;
62     }
63 }