ZOJ 3430 Detect the Virus（AC自动机）

题目链接：http://acm.zju.edu.cn/onlinejudge/showProblem.do?problemCode=3430

题意：给你n个编码后的模式串，和m个编码后的主串，求原来主串中含有模式串的个数

思路：首先要将模式串解码成未编码前来建立ac自动机，然后解码主串扫描统计即可。

code：

 #include <cstdio>
 #include <cstring>
 #include <queue>
 #include <set>
 using namespace std;
 const int KIND = ;
 const int MAXN = ;

 struct Trie
 {
     int next[MAXN][KIND], fail[MAXN], id[MAXN];
     int root, L, num;
     int create()
     {
         for (int i = ; i < KIND; ++i)
             next[L][i] = -;
         return L++;
     }
     void init()
     {
         L = ;
         num = ;
         memset(id, , sizeof(id));
         root = create();
     }
     void insert(unsigned char str[], int len)
     {
         int now = root;
         for (int i = ; i < len; ++i)
         {
             if (- == next[now][str[i]])
                 next[now][str[i]] = create();
             now = next[now][str[i]];
         }
         id[now] = ++num;
     }
     void build()
     {
         queue<int>Q;
         fail[root] = root;
         for (int i = ; i < KIND; ++i)
         {
             if (- == next[root][i])
                 next[root][i] = root;
             else
             {
                 fail[next[root][i]] = root;
                 Q.push(next[root][i]);
             }
         }
         while (!Q.empty())
         {
             int now = Q.front();
             Q.pop();
             for (int i = ; i < KIND; ++i)
             {
                 if (- == next[now][i])
                     next[now][i] = next[fail[now]][i];
                 else
                 {
                     fail[next[now][i]] = next[fail[now]][i];
                     Q.push(next[now][i]);
                 }
             }
         }
     }
     int query(unsigned char str[], int len)
     {
         set<int>S;
         int now = root;
         for (int i = ; i < len; ++i)
         {
             now = next[now][str[i]];
             int temp = now;
             while (temp != root)
             {
                 if (id[temp]) S.insert(id[temp]);
                 temp = fail[temp];
             }
         }
         return (int)S.size();
     }
 };

 Trie ac;
 char buf[];
 unsigned char temp[];
 unsigned char str[];

 unsigned char Tran(char ch)
 {
     if (ch >= 'A' && ch <= 'Z') return ch - 'A';
     if (ch >= 'a' && ch <= 'z') return ch - 'a' + ;
     if (ch >= '' && ch <= '') return ch - '' + ;
     if (ch == '+') return ;
     return ;
 }

 int Decode(int len)
 {
     int k = ;
     for (int i = ; i < len; i += )
     {
         str[k++] = (temp[i]<<)|(temp[i + ]>>);
         if (i +  < len) str[k++] = (temp[i + ]<<)|(temp[i + ]>>);
         if (i +  < len) str[k++] = (temp[i + ]<<)|(temp[i + ]);
     }
     return k;
 }

 int main()
 {
     int n, m;
     while (scanf("%d", &n) != EOF)
     {
         ac.init();
         for (int i = ; i <n; ++i)
         {
             scanf("%s", buf);
             int len = strlen(buf);
             while ('=' == buf[len - ]) --len;
             for (int j = ; j < len; ++j) temp[j] = Tran(buf[j]);
             ac.insert(str, Decode(len));
         }
         ac.build();
         scanf("%d", &m);
         for (int i = ; i < m; ++i)
         {
             scanf("%s", buf);
             int len = strlen(buf);
             while ('=' == buf[len - ]) --len;
             for (int j = ; j < len; ++j) temp[j] = Tran(buf[j]);
             printf("%d\n", ac.query(str, Decode(len)));
         }
         printf("\n");
     }
     return ;
 }