AC自动机 P3808

前置知识：

1.KMP

2.Trie

其实我就是来贴个代码的好吧。

代码主要内容：

1.建Trie树

2.Getfail（得到fail值）

3.query

#include <bits/stdc++.h>
using namespace std;
const int N = 1e7 + 5;
int n;
char s[N];
int Trie[N][27], val[N], fail[N];
int cnt = 0;

void build(void)
{
    int len = strlen(s);
    int now = 0;
    for (int i = 0; i < len; i++)
    {
        if (!Trie[now][s[i] - 'a'])
        {
            Trie[now][s[i] - 'a'] = ++cnt;
        }
        now = Trie[now][s[i] - 'a'];
    }
    val[now]++;
    return;
}

void Getfail(void)
{
    queue<int> q;
    for (int i = 0; i < 26; i++)
    {
        if (Trie[0][i])
        {
            fail[Trie[0][i]] = 0;
            q.push(Trie[0][i]);
        }
    }
    while (!q.empty())
    {
        int head = q.front();
        q.pop();
        for (int i = 0; i < 26; i++)
        {
            if (Trie[head][i])
            {
                fail[Trie[head][i]] = Trie[fail[head]][i];
                q.push(Trie[head][i]);
            }
            else
                Trie[head][i] = Trie[fail[head]][i];
        }
    }
    return;
}

int query(void)
{
    int len = strlen(s);
    int now = 0, ans = 0;
    for (int i = 0; i < len; i++)
    {
        now = Trie[now][s[i] - 'a'];
        for (int j = now; val[j] != -1; j = fail[j])
            ans += val[j], val[j] = -1;
    }
    return ans;
}

int main(void)
{
    scanf("%d", &n);
    for (int i = 1; i <= n; i++)
    {
        scanf("%s", s);
        build();
    }
    Getfail();
    scanf("%s", s);
    printf("%d
", query());
    return 0;
}