hdU 2222 Keywords Search（AC自动机）

/*ACAC自动机问题参考：http://www.cppblog.com/mythit/archive/2009/04/21/80633.html*/#include <iostream>using namespace std;const int nMax = 1000100;const int mMax = 60;const int Max = 26;struct Node{Node *fail;Node *next[Max];int count;Node(){fail = NULL;memset(next, 0, sizeof(next));count = 0;}}*queue[nMax];char keyWord[mMax];char str[nMax];int ans;void insert(char s[], Node *root)//构建tire树，这里没什么可解释，一次历遍即可{Node *p = root;for(int i = 0; s[i]; ++ i){int index = s[i] - 'a';if(p->next[index] == NULL) p->next[index] = new Node();p = p->next[index];}p ->count ++;}void buildFailNode(Node *root)//构建失败节点，队列实现{int front = 0,rear = 0;queue[front ++] = root;while(rear < front){Node *p = queue[rear ++];for(int i = 0; i < Max; ++ i){if(p->next[i]){Node *fa = p->fail;while(fa != NULL)//不断寻找p的失败节点直到发现fa子节点中也存在i节点{if(fa->next[i]){p->next[i]->fail = fa->next[i];break;}fa = fa->fail;}if(fa == NULL) p->next[i]->fail = root;queue[front ++] = p->next[i];}}}}void match(Node *root)//寻找一串字符中，共有多少能与关键字匹配。{Node *p = root;for(int i = 0; str[i]; ++ i){int index = str[i] - 'a';while(p->next[index] == NULL && p != root)p = p->fail;p = p->next[index];p = (p == NULL) ? root : p;//为了配合while()中p != root的应用Node *_p = p;//这里需要将p另外复制给_p，p的值不能做改动,p此时存储的是第一个匹配的节点while(_p != root && _p->count != -1)//这里使用while循环即可将str[i]位置所有匹配全部找出来{ans += _p->count;_p->count = -1;_p = _p ->fail;}}}int main(){//freopen("e://data.txt", "r", stdin);int T;scanf("%d", &T);while(T --){int n;scanf("%d", &n);Node *root = new Node();while(n --){scanf("%s", keyWord);insert(keyWord, root);}scanf("%s", str);buildFailNode(root);ans = 0;match(root);printf("%d\n", ans);}return 0;}