BZOJ-3940：Censoring（AC自动机裸题）

Farmer John has purchased a subscription to Good Hooveskeeping magazine for his cows, so they have plenty 

of material to read while waiting around in the barn during milking sessions. Unfortunately, the latest 

issue contains a rather inappropriate article on how to cook the perfect steak, which FJ would rather his 

cows not see (clearly, the magazine is in need of better editorial oversight).

FJ has taken all of the text from the magazine to create the string S of length at most 10^5 characters. 

He has a list of censored words t_1 ... t_N that he wishes to delete from S. To do so Farmer John finds 

the earliest occurrence of a censored word in S (having the earliest start index) and removes that instance 

of the word from S. He then repeats the process again, deleting the earliest occurrence of a censored word 

from S, repeating until there are no more occurrences of censored words in S. Note that the deletion of one 

censored word might create a new occurrence of a censored word that didn't exist before.

Farmer John notes that the censored words have the property that no censored word appears as a substring of 

another censored word. In particular this means the censored word with earliest index in S is uniquely 

defined.Please help FJ determine the final contents of S after censoring is complete.

FJ把杂志上所有的文章摘抄了下来并把它变成了一个长度不超过10^5的字符串S。他有一个包含n个单词的列表，列表里的n个单词

记为t_1...t_N。他希望从S中删除这些单词。 

FJ每次在S中找到最早出现的列表中的单词(最早出现指该单词的开始位置最小)，然后从S中删除这个单词。他重复这个操作直到S中

没有列表里的单词为止。注意删除一个单词后可能会导致S中出现另一个列表中的单词 

FJ注意到列表中的单词不会出现一个单词是另一个单词子串的情况，这意味着每个列表中的单词在S中出现的开始位置是互不相同的 

请帮助FJ完成这些操作并输出最后的S

 

Input

The first line will contain S. The second line will contain N, the number of censored words. The next N lines contain the strings t_1 ... t_N. Each string will contain lower-case alphabet characters (in the range a..z), and the combined lengths of all these strings will be at most 10^5.

第一行包含一个字符串S 

第二行包含一个整数N 

接下来的N行，每行包含一个字符串，第i行的字符串是t_i

 

Output

The string S after all deletions are complete. It is guaranteed that S will not become empty during the deletion process.

一行，输出操作后的S

 

 

 

Sample Inputbegintheescapexecutionatthebreakofdawn 2 escape execution

Sample Outputbeginthatthebreakofdawn

题意：给N个字符串，设集合为T，以及一个长字符串S，对于S，一直删第一个字串，如果其存在T集合里，则删去，问删到最后S为？

思路：N个字符串建立AC自动机，然后S在自动机上面跑，如果跑到的位置是“关键点”，则删去，同时跑的位置跑到删去后AC自动机对应的位置。

所以记录当前串和每个长度对应的位置即可。（送分题

#include<bits/stdc++.h>
using namespace std;
const int maxn=100010;
char c[maxn],s[maxn],ans[maxn];
int ch[maxn][26],End[maxn],fail[maxn],q[maxn];
int pos[maxn],dep[maxn],head,tail,cnt;
void insert()
{
    int Now=0,d=0; for(int i=1;c[i];i++){
        d++;
        if(!ch[Now][c[i]-'a']) ch[Now][c[i]-'a']=++cnt,dep[cnt]=d;
        Now=ch[Now][c[i]-'a'];
    }   End[Now]=1;
}
void failbuild()
{
    for(int i=0;i<26;i++) if(ch[0][i]) q[++head]=ch[0][i];
    while(tail<head){
        int Now=q[++tail];
        for(int i=0;i<26;i++){
            if(ch[Now][i]) {
                fail[ch[Now][i]]=ch[fail[Now]][i];
                q[++head]=ch[Now][i];
            }
            else ch[Now][i]=ch[fail[Now]][i];
        }
    }
}
int main()
{
    int N,L,i,j;
    scanf("%s%d",s+1,&N);
    for(i=1;i<=N;i++){
        scanf("%s",c+1);
        insert();
    }
    failbuild();
    int top=0,Now=0;
    for(i=1;s[i];i++){
        ans[++top]=s[i]; 
        Now=ch[Now][s[i]-'a'];
        pos[top]=Now;
        if(End[Now]){
             top-=dep[Now]; Now=pos[top];
        }
    }
    for(i=1;i<=top;i++) printf("%c",ans[i]);
    return 0;
}