POJ-1200 Crazy Search(hash)

 1 #include<stdio.h>
 2 #include<string.h>
 3 #define mem(a) memset(a,0,sizeof(a))
 4 
 5 unsigned int hash[16000000+5];
 6 unsigned int c[128];
 7 char str[1000000];
 8 
 9  int main()
10  {
11      int len,base;
12      while(~scanf("%d%d",&len,&base))
13      {
14          mem(str);
15          mem(c);
16          mem(hash);
17          scanf("%s",str);
18         int num =0;
19          int i,j=0,length=strlen(str),tp=1;
20          for(i=0;i<length;i++)
21         {
22              if(c[str[i]]==0)c[str[i]]=++j;
23              if(j==base)break;
24          }
25          for(i=0;i<len;i++)
26          {
27              num=num*base+c[str[i]]-1;
28              tp*=base;
29          }
30          tp/=base;
31          hash[num]=1;
32          int count=1;
33          for(i=1;i<=length-len;i++)
34          {
35             num = ( num-(c[str[i-1]]-1)*tp )* base+ c[str[i+len-1]] - 1;
36              if(!hash[num])
37              {
38                  hash[num]=1;
39                  count++;
40              }
41          }
42          printf("%d\n",count);
43      }
44      return 0;
45  }