hdu2896(ac自动机)

题目链接: http://acm.hdu.edu.cn/showproblem.php?pid=2896

题意: 中文题诶~

思路: ac自动机

这里要求记录匹配的模式串的编号, 不过题目中说明了不同模式串对应的编号是不同的, 所以可以直接用 end 数组记录编号即可, 然后与主串匹配成功的标记一下即可.

代码:

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

const int MAXN = 500 * 200 + 10;
int sol[510];

struct Trie{
    int next[MAXN][128], fail[MAXN], end[MAXN];
    int root, L;
    int newnode(){//初始化字典树节点
        for(int i = 0; i < 128; 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[], int id){//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]] == -1) next[now][buf[i]] = newnode();
            now = next[now][buf[i]];
        }
        end[now] = id;//记录编号
    }
    void build(){ //构造fail数组
        queue<int> Q;
        fail[root] = root;
        for(int i = 0; i < 128; 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 < 128; 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]);
            }
        }
    }
    bool query(char buf[]){
        int len = strlen(buf);
        int now = root;
        bool flag = false;
        for(int i = 0; i < len; i++){
            now = next[now][buf[i]];
            int temp = now;
            while(temp != root){
                if(end[temp]){
                    sol[end[temp]] = 1;
                    flag = true;
                }
                temp = fail[temp];
            }
        }
        return flag;
    }
    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];

int main(void){
    int n, m;
    while(~scanf("%d", &n)){
        ac.init();
        int tot = 0;
        for(int i = 1; i <= n; i++){
            scanf("%s", buf);
            ac.insert(buf, i);
        }
        ac.build();
        scanf("%d", &m);
        for(int i = 1; i <= m; i++){
            scanf("%s", buf);
            bool flag = ac.query(buf);
            if(flag){
                tot += 1;
                printf("web %d:", i);
                for(int j = 1; j <= n; j++){
                    if(sol[j]){
                        sol[j] = 0;
                        printf(" %d", j);
                    }
                }
                puts("");
            }
        }
        printf("total: %d
", tot);
    }
    return 0;
}