[Bzoj1195][HNOI2006]最短母串(AC自动机)

题目链接：https://www.lydsy.com/JudgeOnline/problem.php?id=1195

多个字符串匹配问题用AC自动机没跑了，建好AC自动机后，由于要求答案要最短和字典序最小，则在AC自动机上状压bfs搜索，bfs保证搜到的串长度最短，然后每次从A-Z遍历，保证搜到的字典序最小。状态压缩成在AC自动机上节点i时，包含了串的状态为j，最后状态为(1<<n)-1时停止。

偷偷懒用cin...

 1 #include<bits/stdc++.h>
 2 using namespace std;
 3 typedef long long ll;
 4 int n;
 5 bool vis[610][4100];
 6 struct node {
 7     int num, st;
 8     string ans;
 9 };
10 struct ACzd {
11     int AC[610][26];
12     int fail[610];
13     int numend[610];
14     int len, root;
15     int newcode() {
16         memset(AC[len], 0, sizeof(AC[len]));
17         numend[len] = 0;
18         return len++;
19     }
20     void init() {
21         len = 0;
22         root = newcode();
23     }
24     void build(char *s, int id) {
25         int k = strlen(s);
26         int now = root;
27         for (int i = 0; i < k; i++) {
28             if (AC[now][s[i] - 'A'] == 0)
29                 AC[now][s[i] - 'A'] = newcode();
30             now = AC[now][s[i] - 'A'];
31         }
32         numend[now] |= (1 << id);
33     }
34     void get_fail() {
35         fail[root] = root;
36         queue<int>q;
37         for (int i = 0; i < 26; i++) {
38             if (AC[root][i] != 0) {
39                 fail[AC[root][i]] = root;
40                 q.push(AC[root][i]);
41             }
42             else
43                 AC[root][i] = root;
44         }
45         while (!q.empty()) {
46             int now = q.front();
47             q.pop();
48             numend[now] |= numend[fail[now]];
49             for (int i = 0; i < 26; i++) {
50                 if (AC[now][i] != 0) {
51                     fail[AC[now][i]] = AC[fail[now]][i];
52                     q.push(AC[now][i]);
53                 }
54                 else
55                     AC[now][i] = AC[fail[now]][i];
56             }
57         }
58     }
59     string solve() {
60         queue<node>q;
61         int endst = (1 << n) - 1;
62         q.push({ root,0,"" });
63         while (!q.empty()) {
64             node p = q.front();
65             q.pop();
66             if (p.st == endst) {
67                 return p.ans;
68             }
69             for (int i = 0; i < 26; i++) {
70                 int Nextnum = AC[p.num][i];
71                 int Nextst = p.st | numend[Nextnum];
72                 if (!vis[Nextnum][Nextst]) {
73                     vis[Nextnum][Nextst] = 1;
74                     q.push({ Nextnum,Nextst,p.ans + (char)(i + 'A') });
75                 }
76             }
77         }
78     }
79 }AC;
80 char s[55];
81 int main() {
82     ios::sync_with_stdio(0);
83     while (cin >> n) {
84         AC.init();
85         for (int i = 0; i < n; i++) {
86             cin >> s;
87             AC.build(s, i);
88         }
89         AC.get_fail();
90         string ans = AC.solve();
91         cout << ans << endl;
92     }
93 }

 

posted @ 2019-07-04 09:01  祈梦生  阅读(158)  评论(0)  编辑  收藏  举报