HDU 2896 病毒侵袭（AC自动机）

题目连接：http://acm.hdu.edu.cn/showproblem.php?pid=2896

题意：给你n个模式串，m个主串，求出每个主串中出现的模式串的标号。

思路：AC自动机水题，trie树中维护标号，m次扫描即可，注意点输出格式。

code：

  1 #include <cstdio>

  2 #include <cstring>

  3 #include <queue>

  4 #include <set>

  5 using namespace std;

  6 const int MAXN = 10005;

  7 const int KIND = 128;

  8 

  9 struct node

 10 {

 11     int id;

 12     node* fail;

 13     node* next[KIND];

 14     node()

 15     {

 16         id = 0;

 17         fail = NULL;

 18         for (int i = 0; i < KIND; ++i) next[i] = NULL;

 19     }

 20 };

 21 node* root;

 22 int L = 0;

 23 char str[MAXN];

 24 set<int> ans;

 25 

 26 void Insert(char str[])

 27 {

 28     node* temp = root;

 29     int len = strlen(str);

 30     for (int i = 0; i < len; ++i)

 31     {

 32         if (temp->next[str[i]] == NULL)

 33             temp->next[str[i]] = new node();

 34         temp = temp->next[str[i]];

 35     }

 36     temp->id = ++L;

 37 }

 38 

 39 void Build()

 40 {

 41     queue<node*>Q;

 42     root->fail = root;

 43     for (int i = 0; i < KIND; ++i)

 44     {

 45         if (root->next[i] == NULL)

 46             root->next[i] = root;

 47         else

 48         {

 49             root->next[i]->fail = root;

 50             Q.push(root->next[i]);

 51         }

 52     }

 53     while (!Q.empty())

 54     {

 55         node* temp = Q.front();

 56         Q.pop();

 57         for (int i = 0; i < KIND; ++i)

 58         {

 59             if (temp->next[i] == NULL)

 60                 temp->next[i] = temp->fail->next[i];

 61             else

 62             {

 63                 temp->next[i]->fail = temp->fail->next[i];

 64                 Q.push(temp->next[i]);

 65             }

 66         }

 67     }

 68 }

 69 

 70 int Query(char str[])

 71 {

 72     node* temp = root;

 73     int len = strlen(str);

 74     ans.clear();

 75     for (int i = 0; i < len; ++i)

 76     {

 77         while (temp->next[str[i]] == NULL && temp != root) temp = temp->fail;

 78         temp = temp->next[str[i]];

 79         if (temp == NULL) temp = root;

 80         node* x = temp;

 81         while (x != root)

 82         {

 83             if (x->id != 0) ans.insert(x->id);

 84             x = x->fail;

 85         }

 86     }

 87     return ans.size();

 88 }

 89 

 90 

 91 int main()

 92 {

 93     int n, m;

 94     int tot = 0;

 95     while (scanf("%d", &n) != EOF)

 96     {

 97         root = new node();

 98         for (int i = 0; i < n; ++i)

 99         {

100             scanf("%s", str);

101             Insert(str);

102         }

103         Build();

104         scanf("%d", &m);

105         for (int i = 1; i <= m; ++i)

106         {

107             scanf("%s", str);

108             int num = Query(str);

109             if (num == 0) continue;

110             printf("web %d:", i);

111             set<int>::iterator it;

112             for (it = ans.begin(); it != ans.end(); ++it) printf(" %d", *it);

113             printf("\n");

114             ++tot;

115         }

116         printf("total: %d\n", tot);

117     }

118     return 0;

119 }

 数组实现：

  1 #include <cstdio>

  2 #include <cstring>

  3 #include <queue>

  4 #include <set>

  5 using namespace std;

  6 const int KIND = 128;

  7 const int MAXN = 100005;

  8 const int MAXM = 10005;

  9 

 10 struct Trie

 11 {

 12     int next[MAXN][KIND], fail[MAXN], id[MAXN];

 13     int root, L, num;

 14     set<int> ans;

 15     int create()

 16     {

 17         for (int i = 0; i < KIND; ++i)

 18             next[L][i] = -1;

 19         id[L++] = 0;

 20         return L - 1;

 21     }

 22     void init()

 23     {

 24         num = 0;

 25         L = 0;

 26         root = create();

 27     }

 28     void insert(char str[])

 29     {

 30         int now = root;

 31         int len = strlen(str);

 32         for (int i = 0; i < len; ++i)

 33         {

 34             if (-1 == next[now][str[i]])

 35                 next[now][str[i]] = create();

 36             now = next[now][str[i]];

 37         }

 38         id[now] = ++num;

 39     }

 40     void build()

 41     {

 42         queue<int>Q;

 43         fail[root] = root;

 44         for (int i = 0; i < KIND; ++i)

 45         {

 46             if (-1 == next[root][i])

 47                 next[root][i] = root;

 48             else

 49             {

 50                 fail[next[root][i]] = root;

 51                 Q.push(next[root][i]);

 52             }

 53         }

 54         while (!Q.empty())

 55         {

 56             int now = Q.front();

 57             Q.pop();

 58             for (int i = 0; i < KIND; ++i)

 59             {

 60                 if (-1 == next[now][i])

 61                     next[now][i] = next[fail[now]][i];

 62                 else

 63                 {

 64                     fail[next[now][i]] = next[fail[now]][i];

 65                     Q.push(next[now][i]);

 66                 }

 67             }

 68         }

 69     }

 70     int query(char str[])

 71     {

 72         ans.clear();

 73         int now = root;

 74         int len = strlen(str);

 75         for (int i = 0; i < len; ++i)

 76         {

 77             now = next[now][str[i]];

 78             int temp = now;

 79             while (temp != root)

 80             {

 81                 if (id[temp]) ans.insert(id[temp]);

 82                 temp = fail[temp];

 83             }

 84         }

 85         return (int)ans.size();

 86     }

 87 };

 88 Trie ac;

 89 char str[MAXM];

 90 int main()

 91 {

 92     int n, m, tot;

 93     while (scanf("%d", &n) != EOF)

 94     {

 95         ac.init();

 96         tot = 0;

 97         for (int i = 0; i < n; ++i)

 98         {

 99             scanf("%s", str);

100             ac.insert(str);

101         }

102         ac.build();

103         scanf("%d", &m);

104         for (int i = 1; i <= m; ++i)

105         {

106             scanf("%s", str);

107             if (0 == ac.query(str)) continue;

108             printf("web %d:", i);

109             set<int>::iterator it;

110             for (it = ac.ans.begin(); it != ac.ans.end(); ++it) printf(" %d", *it);

111             printf("\n");

112             ++tot;

113         }

114         printf("total: %d\n", tot);

115     }

116     return 0;

117 }