bzoj3524 [Poi2014]Couriers

 1 #include<cstdio>
 2 #include<vector>
 3 #include<ctime>
 4 #include<cstdlib>
 5 #define pb push_back
 6 using namespace std;
 7 const int N =610100;
 8 int n,m,i,j,a,b,c,v[N],ans,vis[N],stack[N],top;
 9 vector<int> vec[N];
10 int ef(int x,int y)
11 {
12     int l,r,m;
13     l=0;
14     r=vec[y].size()-1;
15     while (l<=r)
16     {
17         m=(l+r)>>1;
18         if (vec[y][m]>x) r=m-1;else l=m+1;
19     }
20     return r;
21 } 
22 int main()
23 {
24     srand(12345678);  
25     scanf("%d%d",&n,&m);
26     for (i=1;i<=n;i++)
27     {
28         scanf("%d",&v[i]);
29         vec[v[i]].pb(i);
30     }
31     for (i=1;i<=m;i++)
32     {
33         scanf("%d%d",&a,&b);
34         
35         ans=0;top=0;
36         for (j=1;j<=25;j++)
37         {
38             c=v[a+rand()%(b-a+1)];
39             if (!vis[c])
40             {
41                 vis[c]=1;stack[++top]=c;
42                 if (ef(b,c)-ef(a-1,c)>(b-a+1)/2) 
43                 {
44                     ans=c;break;
45                 }
46             }
47         }
48         for (j=1;j<=top;j++) vis[stack[j]]=0;
49         printf("%d\n",ans);
50     }
51 }