C++-POJ1200-Crazy Search[hash]

Since the character has been given only NC species, it can handle as a string of hexadecimal numbers NC , this construction hash function on it

 1 #include <set>
 2 #include <map>
 3 #include <cmath>
 4 #include <queue>
 5 #include <vector>
 6 #include <cstdio>
 7 #include <cstdlib>
 8 #include <cstring>
 9 #include <iostream>
10 #include <algorithm>
11 using namespace std;
12 const int MAXN=16000001;
13 char s[MAXN];int hash[MAXN],num[130];
14 int main(){
15     for(int N,NC;scanf("%d%d",&N,&NC)!=EOF;){
16         memset(hash,0,sizeof(hash));
17         memset(num,0,sizeof(num));
18         scanf("%s",s+1);
19         int cnt=0,ans=0,len=strlen(s+1);
20         for(int i=1;i<=len&&cnt<=NC;i++)if(!num[s[i]])num[s[i]]=cnt++;
21         for(int i=1;i<=len-N+1;i++){
22             int hashi=0;for(int j=i;j<=i+N-1;j++)hashi=hashi*NC+num[s[j]];
23             hash[hashi]?0:ans++,hash[hashi]=1;
24         }
25         cout<<ans<<endl;
26     }
27     return 0;
28 }