P3808 模板AC自动机（简单版）

Posted 2022-06-21 acerkoo

题意

AC自动机模版题。

传送门

Code

#include <bits/stdc++.h>

using namespace std;
const int maxn = 1e6+10;

int fail[maxn], e[maxn], tree[maxn][26], tot;
void insert(char *t) 
    int p = 0;
    for (int x, i=0; t[i]; ++i) 
        x = t[i]-'a';
        if(!tree[p][x]) tree[p][x] = ++tot;
        p =  tree[p][x];
    
    ++e[p];

void buildAc() 
    queue<int> q;
    for (int i=0; i<26; ++i) 
        if(tree[0][i])
            q.push(tree[0][i]);
    
    while(!q.empty()) 
        int u = q.front();
        q.pop();
        for (int i=0; i<26; ++i) 
            if(tree[u][i]) fail[tree[u][i]] = tree[fail[u]][i], q.push(tree[u][i]);
            else tree[u][i] = tree[fail[u]][i];
        
    

int query(char *t) 
    int p=0, res=0;
    for (int i=0; t[i]; ++i)  
        p = tree[p][t[i]-'a'];
        for (int i=p; i&&(~e[i]); i=fail[i]) res += e[i], e[i]=-1;
    
    return res;

char str[maxn];

int main() 
    int n;
    scanf("%d", &n);
    for (int i=1; i<=n; ++i) 
        scanf("%s", str);
        insert(str);
    
    buildAc();
    scanf("%s", str);
    printf("%d\n", query(str));
    return 0;