UVA 1619/POJ2796 滑窗算法/维护一个单调栈

 1 #include<iostream>
 2 #include<cstring>
 3 #include<cstdio>
 4 #define ll long long
 5 using namespace std;
 6 ll n;
 7 ll a[100005];
 8 ll sum[100005];
 9 ll l[100005],r[100005];
10 ll ans;
11 int gg;
12 int main()
13 {
14     gg=0;
15     while(scanf("%lld",&n)!=EOF)
16     {
17         if(gg)
18         cout<<endl;
19         gg++;
20     sum[0]=0;
21     ans=-1;
22     int flag=0;
23     for(int i=1;i<=n;i++)
24     {
25         scanf("%lld",&a[i]);
26         sum[i]=sum[i-1]+a[i];
27     }
28     a[0]=-1;a[n+1]=-1;
29     l[1]=1;
30     for(int i=2;i<=n;i++)//关键********
31     {
32         int temp=i-1;
33         while(a[temp]>=a[i])//维护一个递增的序列
34             temp=l[temp]-1;
35         l[i]=temp+1;
36     }
37     r[n]=n;
38     for (int i=n-1;i>=1;i--)
39     {
40         int temp=i+1;
41         while(a[temp]>=a[i])
42             temp=r[temp]+1;
43         r[i]=temp-1;
44     }
45     for(int i=1;i<=n;i++)
46     {
47         ll ggg=(sum[r[i]]-sum[l[i]-1])*a[i];
48         if(ggg>ans)
49             flag=i;
50         ans=max(ans,ggg);
51     }
52     printf("%lld\n",ans);
53     printf("%lld %lld\n",l[flag],r[flag]);
54     }
55     return 0;
56 }