HDU-2222 Keywords Search （AC自动机模板）

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题目链接：https://vjudge.net/problem/HDU-2222
#include<bits/stdc++.h> //万能头文件，POJ不支持，其他大部分OJ都支持 using namespace std;const int maxn = 1e7 + 5;const int MAX = 10000000;int cnt;struct node{    node *next[26];    node *fail;    int sum;};node *root;char key[70];node *q[MAX];int head,tail;node *newnode;char pattern[maxn];int N;void Insert(char *s) //构造字典树 {    node *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++;}void build_fail_pointer() //匹配失陪指针fail，相当于KMP的next[] {    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; //递归查找，类似KMP的思想                     }                    if(p == NULL) temp->next[i]->fail = root;                }                q[tail++] = temp->next[i];            }        }    }}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;           }           else break;           temp = temp->fail; //递归加入所有的后缀匹配         }    }}int main(){    int T;    scanf("%d",&T);    while(T--)    {        root=(struct node *)malloc(sizeof(struct node));        for(int j=0;j<26;j++) root->next[j] = 0;        root->fail = 0;        root->sum = 0;        scanf("%d",&N);        getchar();        for(int i = 1; i <= N; i++)        {            gets(key);            Insert(key);        }        gets(pattern);        cnt = 0;        build_fail_pointer();        ac_automation(pattern);        printf("%d\n",cnt);    }    return 0;}
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