HDU2222_Keywords Search _AC自动机模板题

题意

给出若干单词和一串字符，问这串字符中出现了给出单词中的几个。

思路

AC自动机模板题
AC自动机学习资料：
kuangbin大神的blog：http://www.cppblog.com/mythit/archive/2009/04/21/80633.html
包括AC代码中的第二种，也是直接从这里抄过来的

题目链接

http://acm.hdu.edu.cn/showproblem.php?pid=2222

AC代码

这里代码有两版，第二个是照抄的kuangbin大神的，第二版稍微进行了一些改动，只是更靠近自己的风格，几乎可以说完全一样。

版本一

#include<iostream>#include<cstdio>#include<cstring>using namespace std;const int kind = 26;struct node{    node *fail;                                                     //fail指针    node *next[kind];                                               //子节点指针    int count;                                                      //当前节点代表的单词个数    node()    {        fail = NULL;        count = 0;        memset(next, NULL, sizeof next);    }};node *q[500001];                                                    //队列int head, tail;                                                     //队列的首尾指针char keyword[51];                                                   //单词表char str[1000001];                                                  //模式串void insert(char *str, node *root)                                  //将单词插入字典树中{    node *p = root;    int i = 0;    while(str[i])    {        int index = str[i] - 'a';        if(p->next[index] == NULL) p->next[index] = new node();        p = p->next[index];        i ++;    }    p->count ++;}void build_ac_automation(node *root){    head = tail = 0;    q[head ++] = root;    while(head != tail)    {        node *temp = q[tail ++];        node *p = NULL;        for(int i= 0; i< 26; i++)                                   //线序遍历子树        {            if(temp->next[i] != NULL)            {                p = temp->fail;                while(p != NULL)                                    //沿着fail链找到一个与当前位置对应的位置，构造fail链                {                    if(p->next[i] != NULL)                    {                        temp->next[i]->fail = p->next[i];                        break;                    }                    p = p->fail;                }                if(p == NULL) temp->next[i]->fail = root;           //加边失败，fail指针指向root                q[head ++] = temp->next[i];                         //子节点入队            }        }    }}int query(node *root){    int i = 0, cnt = 0, len = strlen(str);    node *p = root;    while(str[i])                                                   //遍历模式串    {        int index = str[i] - 'a';        while(p->next[index] == NULL && p != root) p = p->fail;     //沿着fail链找一个能继续匹配的树枝，找到root也要停止        p = p->next[index];        if(p == NULL) p = root;                                     //查找失败，p置为root        node *temp = p;                                             //沿着fail链检查是否有单词被构成        while(temp != root && temp->count != -1)                    //-1表示该单词已经被找过一次了        {            cnt += temp->count;            temp->count = -1;            temp = temp->fail;        }        i ++;    }    return cnt;}int main(){    int n, t;    scanf("%d", &t);    while(t --)    {        node *root = new node();        scanf("%d", &n);        getchar();        while(n --)        {            gets(keyword);            insert(keyword, root);        }        build_ac_automation(root);        scanf("%s", str);        printf("%d\n", query(root));    }    return 0;}

版本二

#include<iostream>#include<cstdio>#include<cstring>using namespace std;const int kind = 26;struct node{    node *fail;    node *next[kind];    int count;    node()    {        fail = NULL;        count = 0;        memset(next, NULL, sizeof next);    }} *q[500001];char keyword[51];char str[1000001];int head, tail;void insert(char *str, node *root){    node *p = root;    int i = 0, index;    while(str[i])    {        index = str[i] - 'a';        if(p->next[index] == NULL) p->next[index] = new node();        p = p->next[index];        i ++;    }    p->count ++;}void build_ac_automation(node *root){    int i;    root->fail = NULL;    q[head ++] = root;    while(head != tail)    {        node *temp = q[tail ++];        node *p = NULL;        for(int i= 0; i< 26; i++)        {            if(temp->next[i] != NULL)            {                if(temp == root) temp->next[i]->fail = root;                else{                    p = temp->fail;                    while(p != NULL)                    {                        if(p->next[i] != NULL)                        {                            temp->next[i]->fail = p->next[i];                            break;                        }                        p = p->fail;                    }                    if(p == NULL) temp->next[i]->fail = root;                }                q[head ++] = temp->next[i];            }        }    }}int query(node *root){    int i = 0, cnt = 0, index, len = strlen(str);    node *p = root;    while(str[i])    {        index = str[i] - 'a';        while(p->next[index] == NULL && p != root) p = p->fail;        p = p->next[index];        p = (p == NULL) ? root : p;        node *temp = p;        while(temp != root && temp->count != -1)        {            cnt += temp->count;            temp->count = -1;            temp = temp->fail;        }        i ++;    }    return cnt;}int main(){    int n, t;    scanf("%d", &t);    while(t --)    {        head = tail = 0;        node *root = new node();        scanf("%d", &n);        getchar();        while(n --)        {            gets(keyword);            insert(keyword, root);        }        build_ac_automation(root);        scanf("%s", str);        printf("%d\n", query(root));    }    return 0;}