Poj1200题解

 1 import java.io.BufferedReader;
 2 import java.io.IOException;
 3 import java.io.InputStreamReader;
 4 
 5 public class Poj1200 {
 6 
 7     public static void main(String[] args) throws IOException {
 8         // TODO Auto-generated method stub
 9 
10         BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
11         String[] strArgs = br.readLine().split(" ");
12         
13         boolean[] hash = new boolean[16000000];
14         
15         int N = Integer.parseInt(strArgs[0]);
16         int NC = Integer.parseInt(strArgs[1]);
17         
18         int[] charToInt = new int[260];//保留一个字节，八位的空间0-256表示ansii码的值
19     
20         int seed = 0;
21         String text = br.readLine();
22     
23         for(int i = 0;i<text.length();i++)
24         {
25             if(charToInt[text.charAt(i)]==0)
26             {
27                 charToInt[text.charAt(i)] = seed++;//对每个新出现的字符赋予数字表示
28             };
29         }
30         
31         int index = 0;
32         int temp =0;
33         int t = 1;
34         for(int i = 0;i<N;i++)
35         {
36             temp = temp * NC + charToInt[text.charAt(i)];//计算第一个N位的字符串的NC精制数字表示
37             t *= NC;//
38         }
39         if(!hash[temp])
40         {
41             hash[temp] = true;
42             index++;
43         }
44         
45         int ilength = text.length()-N;
46         for(int i = 1;i<=ilength;i++)
47         {
48             temp = (temp*NC + charToInt[text.charAt( i + N-1)])%t;//去除temp的最高位，补上新偏移到的最低位
49             if(!hash[temp])
50             {
51                 hash[temp] = true;
52                 index++;
53             }
54         }
55         System.out.println(index);
56     }
57 
58 }