BZOJ 3940 Censoring

#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
#include<queue>
#define maxn 500050
using namespace std;
char t[maxn],s[maxn];
int cases,l,son[maxn][30],fail[maxn],fath[maxn],root,tot=0,pre[maxn],ts[maxn],len[maxn];
queue <int> q;
bool flag[maxn];
void insert()
{
    int now=root;
    for (int i=0;i<l;i++)
    {
        int nb=s[i]-‘a‘+1;
        if (!son[now][nb]) son[now][nb]=++tot;
        now=son[now][nb];
        if (i==l-1) len[now]=l;
    }
}
void build_AC()
{
    q.push(root);
    while (!q.empty())
    {
        int head=q.front();q.pop();
        for (int i=1;i<=26;i++)
        {
            if (son[head][i])
            {
                if (head!=root)fail[son[head][i]]=son[fail[head]][i];
                else fail[son[head][i]]=root;
                q.push(son[head][i]);
            }
            else son[head][i]=son[fail[head]][i];
        }
    }
}
void match_AC()
{
    int now=root;ts[0]=1;
    for (int i=1;i<=l;i++)
    {
        int nb=t[i-1]-‘a‘+1;
        while (now!=root && !son[now][nb]) now=fail[now];
        if (son[now][nb]) now=son[now][nb];
        ts[i]=now;
        if (len[now])
        {
            int p=i;
            for (int j=1;j<=len[now];j++)
            {
                flag[p-1]=true;
                p=pre[p];
            }
            pre[i+1]=p;now=ts[p];
        }
    }
}
int main()
{
    scanf("%s",t);
    scanf("%d",&cases);root=tot=0;
    for (int i=1;i<=cases;i++)
    {
        scanf("%s",s);
        l=strlen(s);insert();
    }
    build_AC();
    l=strlen(t);for (int i=1;i<=l;i++) pre[i]=i-1;
    match_AC();
    for (int i=0;i<l;i++)
        if (!flag[i]) printf("%c",t[i]);
    printf("\n");
    return 0;
}