求一個字符串上有多少個匹配的單詞

看著卿學姐的板子寫的

#include <iostream>
#include <cstdio>
#include <sstream>
#include <cstring>
#include <map>
#include <set>
#include <vector>
#include <stack>
#include <queue>
#include <algorithm>
#include <cmath>
#define
 
 rap(i, a, n) for(int i=a; i<=n; i++)
#define rep(i, a, n) for(int i=a; i<n; i++)
#define lap(i, a, n) for(int i=n; i>=a; i--)
#define lep(i, a, n) for(int i=n; i>a; i--)
#define MOD 2018
#define LL long long
#define ULL unsigned long long
#define Pair pair<int, int>
#define mem(a, b) memset(a, b, sizeof(a))
#define
 
 _  ios_base::sync_with_stdio(0),cin.tie(0)
//freopen("1.txt", "r", stdin);
using namespace std;
const int maxn = 1000010, maxm = 500005, INF = 0x7fffffff;
int tot;
queue<int> q;

struct state
{
    int next[26];
    int fail, cnt;
}trie[500005];


void init()
{
    while(!q.empty()) q.pop();
    for(int i=0; i<maxm; i++)
    {
        mem(trie[i].next, 
 
0);
        trie[i].fail = trie[i].cnt = 0;
    }
    tot = 0;
}

void insert(char *s)
{
    int  n = strlen(s);
    int rt = 0;
    for(int i=0;i<n; i++)
    {
        int x = s[i] - ‘a‘;
        if(!trie[rt].next[x])
        {
            trie[rt].next[x] = ++tot;
        }
        rt = trie[rt].next[x];
    }
    trie[rt].cnt++;
}

void build()
{
    trie[0].fail= -1;
    q.push(0);
    while(!q.empty())
    {
        int u = q.front(); q.pop();
        for(int i=0; i<26; i++)
        {
            if(trie[u].next[i])
            {
                if(u == 0) trie[trie[u].next[i]].fail  = 0;
                else{
                    int v = trie[u].fail;
                    while(v != -1)
                    {
                        if(trie[v].next[i])
                        {
                            trie[trie[u].next[i]].fail = trie[v].next[i];
                            break;
                        }
                        v = trie[v].fail;
                    }
                    if(v == -1) trie[trie[u].next[i]].fail = 0;
                }
                q.push(trie[u].next[i]);
            }
        }
    }
}

int Get(int u)
{
    int res = 0;
    while(u)
    {
        res = res + trie[u].cnt;
        trie[u].cnt = 0;
        u = trie[u].fail;
    }
    return res;
}



int math(char *s)
{
    int n = strlen(s);
    int rt = 0, res = 0;
    for(int i=0; i<n; i++)
    {
        int x = s[i] - ‘a‘;
        if(trie[rt].next[x])    //如果有兒子 就直接下傳
            rt = trie[rt].next[x];
        else                    //如果沒有  就去fail去找
        {
            int p = trie[rt].fail;
            while(p != -1 && trie[p].next[x] == 0) p = trie[p].fail;
            if(p == -1) rt = 0; //一直沒找到 則返回祖結點
            else rt = trie[p].next[x];
        }
        if(trie[rt].cnt)    //如果以這個點為後綴的串還沒有被匹配 則匹配
            res = res + Get(rt);
    }
    return res;

}

int T, n;
char s[maxn];
int main()
{
    scanf("%d", &T);
    while(T--)
    {
        init();
        scanf("%d", &n);
        rap(i, 1, n)
        {
            scanf("%s", s);
            insert(s);
        }
        build();
        scanf("%s", s);
        printf("%d\n", math(s));
    }
    return 0;
}

Keywords Search HDU - 2222（ac自動機板題。。）