poj1200-Crazy Search(hash入门经典)

Posted 2021-01-02 hemeiwolong

参考：https://www.cnblogs.com/My-Sunshine/p/4934362.html

https://blog.csdn.net/tomcmd/article/details/48101857

 1 #include <iostream>
 2 #include <cstdio>
 3 #include <cstring>
 4 using namespace std;
 5 const int N=16*1e6+10;
 6 int n,nc;
 7 int hashmap[300];//hash表，存字符的nc进制数
 8 bool vis[N];//标记查重
 9 char s[N];
10 int main()
11 {
12 //    freopen("bin.txt","r",stdin);
13     while (scanf("%d %d",&n,&nc)!=EOF)
14     {
15         scanf("%s",s);
16         memset(vis,0,sizeof(vis));
17         memset(hashmap,0,sizeof(hashmap));
18         int len=strlen(s);
19         int k=0;
20         for (int i=0;i<len;i++)
21         {
22             if (!hashmap[s[i]])//转换为nc进制数
23             {
24                 hashmap[s[i]]=k++;
25             }
26         }
27         int ans=0;
28         for (int i=0;i<len-n+1;i++)
29         {
30             int temp=0;
31             for (int j=i;j<i+n;j++)
32             {
33                 temp=temp*nc+hashmap[s[j]];//注意转化公式不要写错！
34             }
35             if (!vis[temp])
36             {
37                 ans++;
38                 vis[temp]=true;
39             }
40         }
41         printf("%d
",ans);
42     }
43 
44     return 0;
45 }