我用的是指针，跑的还挺快的，但是不知道为什么最后几个点会莫名其妙的就RE了。

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#include <bits/stdc++.h>
const int N = 2e6;
int n, m; char str[N];
struct node {
    node *ch[28];
    int v, end;
    node (int v = 0) : v(v) {
        memset(ch, 0, sizeof(ch));
    }
};
node *root = new node(114514);
void insert(char *str)
{
    int n = strlen(str + 1);
    auto now = root;
    for (int i = 1; i <= n; i ++ )
    {
        int x = str[i] - 'a';
        if (now->ch[x] == nullptr) now->ch[x] = new node(x);
        now = now->ch[x];
    }
    now->end ++ ;
}
int f[N];
int query(char *str, int st, int ed)
{
    auto now = root;
    for (int i = st; i <= ed; i ++ ) 
    {
        int x = str[i] - 'a';
        if (now->ch[x] == nullptr) return 0;
        now = now->ch[x];
        if (now->end >= 1)
            f[i] = 1;
    }
    return now->end;
}
auto main() -> signed
{
    std::cin.tie(nullptr) -> sync_with_stdio(false);
    std::cin >> n >> m;
    for (int i = 1; i <= n; i ++ ) 
    {
        std::cin >> (str + 1);
        insert(str);
    }
    f[0] = 1;
    while (m -- )
    {
        std::cin >> (str + 1);
        int length = strlen(str + 1);
        for (int i = 1; i <= length; i ++ ) {
            f[i] = 0;
        }
        for (int i = 0; i < length; i ++ ) {
            if (f[i]) query(str, i + 1, length);
        }
        for (int i = length; i >= 0; i -- )
            if (f[i]) {
                std::cout << i << std::endl;
                break;
            }
    }
    return 0;
}