hdu2222(ac自动机模板)

先推荐两篇写的很好的ac自动机blog:

http://blog.csdn.net/creatorx/article/details/71100840

http://blog.csdn.net/niushuai666/article/details/7002823

正题

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

题意: 给出 n 个模式串以及一个 主串, 问有多少个模式串在主串中出现过

思路: ac自动机模板题

代码:

#include <iostream>
#include <stdio.h>
#include <string.h>
#include <queue>
using namespace std;

const int MAXN = 5e5 + 10;

struct Trie{
    int next[MAXN][26], fail[MAXN], end[MAXN];
    int root, L;
    int newnode(){//初始化字典树节点
        for(int i = 0; i < 26; i++){
            next[L][i] = -1;
        }
        end[L++] = 0;
        return L - 1;
    }
    void init(){//初始化字典树根节点
        L = 0;
        root = newnode();
    }
    void insert(char buf[]){//往字典树中插入一个单词
        int len = strlen(buf);
        int now = root;
        for(int i = 0; i < len; i++){
            if(next[now][buf[i] - 'a'] == -1) next[now][buf[i] - 'a'] = newnode();
            now = next[now][buf[i] - 'a'];
        }
        end[now]++;
    }
    void build(){ //构造fail数组
        queue<int> Q;
        fail[root] = root;
        for(int i = 0; i < 26; i++){
            if(next[root][i] == -1) next[root][i] = root;
            else{
                fail[next[root][i]] = root;
                Q.push(next[root][i]);
            }
        }
        while(!Q.empty()){
            int now = Q.front();
            Q.pop();
            for(int i = 0; i < 26; i++)
            if(next[now][i] == -1) next[now][i] = next[fail[now]][i];
            else{
                fail[next[now][i]] = next[fail[now]][i];
                Q.push(next[now][i]);
            }
        }
    }
    int query(char buf[]){
        int len = strlen(buf);
        int now = root;
        int res = 0;
        for(int i = 0; i < len; i++){
            now = next[now][buf[i] - 'a'];
            int temp = now;
            while(temp != root){
                res += end[temp];
                end[temp] = 0; // 每个模式串只算一次,所以清0
                temp = fail[temp];
            }
        }
        return res;
    }
    void debug(){
        for(int i = 0; i < L; i++){
            printf("id = %3d,fail = %3d,end = %3d,chi = [",i,fail[i],end[i]);
            for(int j = 0; j < 26; j++){
                printf("%2d",next[i][j]);
            }
            printf("]
");
        }
    }
};

Trie ac;
char buf[MAXN << 1];

int main(void){
    int t, n;
    scanf("%d", &t);
    while(t--){
        ac.init();
        scanf("%d", &n);
        for(int i = 0; i < n; i++){
            scanf("%s", buf);
            ac.insert(buf);
        }
        ac.build();
        scanf("%s", buf);
        printf("%d
", ac.query(buf));
    }
    return 0;
}