HDU5880 Family View(AC自动机)

题意：将匹配的串用‘*’代替

tips:

1 注意内存的使用，据说g++中指针占8字节，c++4字节，所以用g++交会MLE

2 注意这种例子，

1
2
abcd
bc
abc

故失败指针要一直往下走，否则会丢弃一些串

3 当出现非英文字符时应先将指针指向根节点，否则出现

1
1
cy
c,,,,,,,y

时结果为c,,,,,,**(由不止一种Bug造成的),正确的应为c,,,,,,,y，然而很多题解这样也过了~

#include<cstdio>
#include<iostream>
#include<cstdlib>
#include<cstring>
#include<string>
#include<algorithm>
#include<map>
#include<queue>
#include<vector>
#include<cmath>
#include<utility>
using namespace std;
typedef long long LL;
int Hash[128];

const int N = 1000008, CH = 26;
struct Trie{
    Trie *next[CH];
    Trie *fail;
    int len;
};

int flag[N];

char str[N];

class ACauto{

    Trie tree[N];
    private:
        int nxt;
        Trie *root;

    public:
    void init(){
        root = &tree[0];
        nxt=0;
        memset(&tree[0], 0, sizeof(Trie));
        memset(flag, 0, sizeof(flag));
    }

    void insert(char *s){
        Trie *p = root;
        int i;
        for(i = 0; s[i]; i++){
            int c = Hash[s[i]];
            if(!p -> next[c]){
                memset(&tree[++nxt], 0, sizeof(Trie));
                p -> next[c] = &tree[nxt];
            }
            p = p -> next[c];
        }
        //p -> cnt = 1;
        //p -> cnt++;//用于统计
        p -> len = i;

    }

    void build(){
        queue<Trie *> q;
        q.push(root);
        root -> fail = NULL;
        while(!q.empty()){
            Trie *now = q.front();
            q.pop();
            for(int i = 0; i < CH; i++){
                Trie *son = now -> next[i];
                Trie *tp = (now == root)? root: now -> fail->next[i];
                if(son == NULL){
                    now -> next[i] = tp;//Trie图
                }else{
                    son -> fail = tp;
                    //状态合并（如一个串是另一个串的子串则值域可以合并）
                    //son -> cnt += son -> fail -> cnt;
                    q.push(son);
                }
            }
        }
    }

    //查询匹配次数
    void query(char *s){
        Trie *now = root;
        for(int i = 0; s[i]; i++){
            int c = Hash[s[i]];
            if(c == -1){
                //注意,要将now赋值为root
                now = root;
                continue;
            }
            now = now -> next[c];
            Trie *p = now;
            while(p != root){
                if(p -> len){
                    flag[i - p -> len + 1]--;
                    flag[i + 1]++;
                }
                p = p -> fail;
            }

        }
    }
}ac;

int main(){
    fill(Hash, Hash + 128, -1);
    for(int i = ‘a‘; i <= ‘z‘; i++){
        Hash[i] = i - ‘a‘;
    }

    for(int i = ‘A‘; i <= ‘Z‘; i++){
        Hash[i] = i - ‘A‘;
    }

    int t;
    cin >>t;
    while(t--){
        ac.init();
        int n;
        scanf("%d", &n);
        for(int i  = 0; i < n; i++){
            scanf("%s", str);
            ac.insert(str);
        }
        ac.build();
        getchar();
        gets(str);
        ac.query(str);
        LL cnt = 0;
        for(int i = 0; str[i]; i++){
            cnt += flag[i];
            if(cnt >= 0){
                putchar(str[i]);
            }else{
                putchar(‘*‘);
            }

        }
        printf("\n");
    }

    return 0;
}