hdu 5288 OO’s Sequence（2015多校第一场第1题）枚举因子

 1 #include <cstdio>
 2 #include <cstdlib>
 3 #include <cmath>
 4 #include <cstring>
 5 #include <iostream>
 6 #include <queue>
 7 #include <algorithm>
 8 #include <vector>
 9 using namespace std;
10 #define LL __int64
11 #define INF 0x3f3f3f3f
12 const int MAXN=100005;
13 #define mod 1000000007
14 int l[MAXN];
15 int r[MAXN];
16 int a[MAXN];
17 int visl[MAXN];
18 int visr[MAXN];
19 LL ans;
20 int main()
21 {
22     int n,i,j;
23     while(~scanf("%d",&n))
24     {
25         memset(visl,0,sizeof(visl));
26         memset(visr,0,sizeof(visr));
27         for(i=1;i<=n;i++)
28         {
29             scanf("%d",&a[i]);
30             l[i]=1;
31             r[i]=n;
32         }
33         for(i=1;i<=n;i++)
34         {
35             for(j=a[i];j<=10000;j+=a[i])
36             {
37                 if(visr[j]&&r[visr[j]]==n)
38                     r[visr[j]]=i-1;
39             }
40             visr[a[i]]=i;
41         }
42         for(i=n;i>0;i--)
43         {
44             for(j=a[i];j<=10000;j+=a[i])
45             {
46                 if(visl[j]&&l[visl[j]]==1)
47                     l[visl[j]]=i+1;
48             }
49             visl[a[i]]=i;
50         }
51         ans=0;
52         for(i=1;i<=n;i++)
53         {
54             //printf("%d %d\n",l[i],r[i]);
55             ans+=(LL)(i+1-l[i])*(r[i]-i+1);
56             ans%=mod;
57         }
58         printf("%I64d\n",ans%mod);
59     }
60     return 0;
61 }