題目鏈接：http://codeforces.com/problemset/problem/368/B

題目：

Sereja has an array a, consisting of n integers a1, a2, ..., an. The boy cannot sit and do nothing, he decided to study an array. Sereja took a piece of paper and wrote out m integers l1, l2, ..., lm (1 ≤ l

Sereja wrote out the necessary array elements but the array was so large and the boy was so pressed for time. Help him, find the answer for the described question for each l

The first line contains two integers n and m (1 ≤ n, m ≤ 105). The second line contains n integers a1, a2, ..., an (1 ≤ ai ≤ 105) — the array elements.

Next m lines contain integers l1, l2, ..., l

Print m lines — on the i-th line print the answer to the number li.

10 10
1 2 3 4 1 2 3 4 100000 99999
1
2
3
4
5
6
7
8
9
10

6
6
6
6
6
5
4
3
2
1

題解：維護下後綴即可。（標簽為dp，emmm...，大水題

 1 #include <map>
 2 #include <cstdio>
 3 using namespace std;
 4 
 5 const int N=1e5+10;
 6 map <int,int> m;
 7 int f[N],a[N];
 8 
 9 int main(){
10     int n,t,x;
11     scanf("%d %d",&n,&t);
12     for(int i=1;i<=n;i++) scanf("%d",&a[i]);
13     for(int i=n;i>=1;i--){
14         f[i]=f[i+1];
15         if(!m[a[i]]) m[a[i]]=1,f[i]++;
16     }
17     while(t--){
18         scanf("%d",&x);
19         printf("%d\n",f[x]);
20     }
21     return 0;
22 }

CF 368B Sereja and Suffixes（DP？）