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&l
4000
t; 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;
}