POJ 1200

POJ 1200

#include <cstdio>
#include<string>
#include<cstring> 
using namespace std;
bool Hash[16000001];
int w[500];
char s[16000001];
int main(){
    int n,nc,cnt,ans,i,j,l,sum;
    while(~scanf("%d%d",&n,&nc)){
        cnt=0;
        ans=0;
        memset(w,-1,sizeof(w));
        memset(Hash, false, sizeof(Hash));
        scanf("%s",s);
        l=strlen(s);
        for(i=0;i<l&&cnt<nc;i++)
            if(w[s[i]]==-1)
                 w[s[i]]=cnt++;
        for(i=0;i<l-n+1;i++){
            sum=0;
            for(j=i;j<i+n;j++)
                 sum=sum+sum*nc+w[s[j]];
            if(!Hash[sum]){
                 ans++;
                 Hash[sum]=true;
            }
        }
        printf("%d\n",ans);
    }
    return 0;
}