String （套路Hash）

 1 #include <stdio.h>
 2 #include <algorithm>
 3 #include <iostream>
 4 #include <stdlib.h>
 5 #include <string>
 6 #include <string.h>
 7 #include <math.h>
 8 #include <vector>
 9 #include <queue>
10 #include <stack>
11 #include <map>
12 #include <set>
13 
14 
15 #define INF 0x3f3f3f3f
16 #define LL long long
17 
18 typedef unsigned long long ull;
19 const int maxn = 2e5+10;
20 
21 
22 char s[maxn];
23 ull base = 131;
24 ull p[maxn],h[maxn];
25 
26 std::map<ull,int > mp;
27 
28 ull get(int l,int r){
29     return (h[r] - h[l-1]*p[r-l+1]);
30 }
31 
32 int main() {
33     p[0] = 1;
34     for (int i=1;i<maxn;i++) {
35         p[i] = p[i-1] * base;
36     }
37     int m,l;
38     while (~scanf("%d%d",&m,&l)) {
39         scanf("%s",s+1);
40         int len = strlen(s+1);
41         int ans = 0;
42         for (int i=1;i<=len;i++) {
43             h[i] = h[i-1] * base + s[i];
44         }
45         for (int i=1;i<=l && i+m*l-1<=len;i++) {  //枚举长度
46             mp.clear();
47             for (int j=i;j<=i+m*l-1;j+=l) {  // 枚举i+m*l-1之前的长度为l的Hash
48                 ull temp = get(j,j+l-1);
49                 mp[temp]++;
50             }
51             if (mp.size() == m) {
52                 ans++;
53             }
54             for (int j=i+m*l;l+j-1<=len;j+=l) { //枚举i+m*l-1之后的长度为l的Hash
55                 ull temp = get(j-m*l,l+j-m*l-1);
56                 mp[temp]--; // 前面减少一个
57                 if (mp[temp] == 0)
58                     mp.erase(temp);
59                 temp = get(j,j+l-1); // 后面增加一个
60                 ++mp[temp];
61                 if (mp.size() == m)
62                     ans++;
63             }
64         }
65         printf("%d\n",ans);
66     }
67     return 0;
68 }