poj1200-CrazySearch(Rabin-Karp Hash)

#include <cstdio>
#include <cstring>
#include <algorithm>
using namespace std;

#define MAXC    1<<9
#define MAXCH   1<<20
#define MAXN    16000005

char str[MAXCH];
int  val[MAXC];
bool hash[MAXN];

int main(int argc, char const *argv[])
{
#ifndef ONLINE_JUDGE
        freopen("test.in", "r", stdin);
#endif
        int idx, sub_len, diff, rst, len;
        while( ~scanf("%d %d", &sub_len, &diff) ) {
                scanf("%s", str); rst = 0;
                memset(val, -1, sizeof(val)); memset(hash, false, sizeof(hash));
                for(int i = 0, cnt = 0; cnt <= diff && '\0' != str[i]; i ++) {
                        if( -1 != val[str[i]] ) {
                                continue;
                        }
                        val[str[i]] = cnt ++;
                }
                len = strlen(str);
                for(int i = 0; i <= len-sub_len; i ++) { idx = 0;
                        for(int j = i; j < i+sub_len; j ++) {
                                idx = idx*diff+val[str[j]];
                        }
                        if( true == hash[idx] ) {
                                continue;
                        }
                        hash[idx] = true; rst += 1;
                }
                printf("%d\n", rst);
        }
        return 0;
}