AC自动机模板

Posted 2020-09-29 Pacify

struct node
{
    node *next[26];
    node *fail;
    int sum;
};

int cnt;
node *root;

//构造字典树
void Insert(char *s)
{
    node *newnode,*p;
    p = root;
    for(int i = 0; s[i]; i++)
    {
        int x = s[i] - ‘a‘;
        if(p->next[x] == NULL)
        {
            newnode=(struct node *)malloc(sizeof(struct node));
            for(int j=0; j<26; j++) newnode->next[j] = 0;
            newnode->sum = 0;
            newnode->fail = 0;
            p->next[x]=newnode;
        }
        p = p->next[x];
    }
    p->sum++;
}

//BFS构造fail指针
node *q[maxn];
void build_fail_pointer()
{
    int head,tail;
    head = 0;
    tail = 1;
    q[head] = root;
    node *p;
    node *temp;
    while(head < tail)
    {
        temp = q[head++];
        for(int i = 0; i <= 25; i++)
        {
            if(temp->next[i])
            {
                if(temp == root)
                {
                    temp->next[i]->fail = root;
                }
                else
                {
                    p = temp->fail;
                    while(p)
                    {
                        if(p->next[i])
                        {
                            temp->next[i]->fail = p->next[i];
                            break;
                        }
                        p = p->fail;
                    }
                    if(p == NULL) temp->next[i]->fail = root;
                }
                q[tail++] = temp->next[i];
            }
        }
    }
}

//匹配
void ac_automation(char *ch)
{
    node *p = root;
    int len = strlen(ch);
    for(int i = 0; i < len; i++)
    {
        int x = ch[i] - ‘a‘;
        while(!p->next[x] && p != root) p = p->fail;
        p = p->next[x];
        if(!p) p = root;
        node *temp = p;
        while(temp != root)
        {
            if(temp->sum >= 0)
            {
                cnt += temp->sum;
                temp->sum = -1;　　//也可以用vis数组标记
            }
            else break;
            temp = temp->fail;
        }
    }
}