Unique Encryption Keys (思维题 预处理)

 1 #include <iostream>
 2 #include <cstdio>
 3 #include <cstring>
 4 #include <vector>
 5 #include <map>
 6 #define Min(a, b)((a)>(b)?(b):(a))
 7 using namespace std;
 8 const int maxn = 1000000+10;
 9 int a[maxn], f[maxn];
10 
11 int main()
12 {
13     int m, q, b, e, i;
14     while(~scanf("%d%d", &m, &q))
15     {
16         if(m==0&&q==0)
17         break;
18         for(i = 1; i <= m; i++)
19             scanf("%d", &a[i]);
20         memset(f, 0, sizeof(f));
21         map<int, int>mp;
22         f[m] = m+1;
23         mp[a[m]] = m;
24         for(i = m-1; i >=1; i--)
25         {
26             if(mp[a[i]]==0)
27                 f[i] = f[i+1];
28             else
29                 f[i] = Min(mp[a[i]], f[i+1]);
30             mp[a[i]] = i;
31         }
32         while(q--)
33         {
34             scanf("%d%d", &b, &e);
35             if(f[b]>e)
36                 cout<<"OK"<<endl;
37             else
38             cout<<a[f[b]]<<endl;
39         }
40     }
41     return 0;
42 }