poj 3368 Frequent values

http://poj.org/problem?id=3368
 1 #include <cstdio>
 2 #include <cstring>
 3 #include <cmath>
 4 #include <algorithm>
 5 #define maxn 100100
 6 using namespace std;
 7 
 8 int a[maxn],f[maxn][30],n,q,x,y,b[maxn];
 9 
10 int main()
11 {
12     while(scanf("%d",&n)!=EOF)
13     {
14         if(n==0) break;
15         scanf("%d",&q);
16         memset(f,0,sizeof(f));
17         for(int i=1; i<=n; i++)
18         {
19             scanf("%d",&a[i]);
20         }
21         memset(b,0,sizeof(b));
22         for(int i=1; i<=n; i++)
23         {
24             if(i==1)
25             {
26                 b[1]=1;
27                 continue;
28             }
29             if(a[i]==a[i-1])
30             {
31                 b[i]=b[i-1]+1;
32             }
33             else
34                 b[i]=1;
35         }
36         for(int i=1; i<=n; i++)
37         {
38             f[i][0]=b[i];
39         }
40         int m=(int)(log(n*1.0)/(log(2.0)));
41         for(int j=1; j<=m; j++)
42         {
43             for(int i=1; i<=n; i++)
44             {
45                 if(i+(1<<j)-1<=n)
46                 {
47                     f[i][j]=max(f[i][j-1],f[i+(1<<(j-1))][j-1]);
48                 }
49             }
50         }
51         for(int i=0; i<q; i++)
52         {
53             scanf("%d%d",&x,&y);
54             int t=x;
55             while(t<=y&&a[t]==a[t-1])
56                 t++;
57             int k=(int)(log(y-t+1.0)/(log(2.0)));
58             int c=max(f[t][k],f[y-(1<<k)+1][k]);
59             if(t>y) c=0;
60             printf("%d
",max(t-x,c));
61         }
62     }
63     return 0;
64 }
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