Aho-Corasick.cpp

/******************************************************************************

    Aho-Corasick algorithm.

    This code finds all words in the text that contain any of the 
    initially given words. O(len of queries + sum len of initial strings)   


    Based on problem K from here: http://codeforces.ru/gym/100133

******************************************************************************/

#include <iostream>
#include <fstream>
#include <cmath>
#include <algorithm>
#include <vector>
#include <set>
#include <map>
#include <stack>
#include <queue>
#include <cstdlib>
#include <cstdio>
#include <string>
#include <cstring>
#include <cassert>
#include <utility>
#include <iomanip>

using namespace std;

const int MAXN = 105000;

struct node {
    int suff_link, par;
    char c;
    map < char, int > go;
    bool is_word;   

    node() {
        suff_link = -1, par = -1;
        is_word = false;
    }
};

int n;
char s[MAXN];
vector <node> trie;

void trieInsert(char s[MAXN]) {
    int cur_node = 0;
    int len = strlen(s);
    for (int i = 0; i < len; i++) {
        int go = trie[cur_node].go[s[i]];
        if (go == 0) {
            node add;
            add.par = cur_node; add.c = s[i];
            trie.push_back(add);
            go = (int) trie.size() - 1;
            trie[cur_node].go[s[i]] = go;
        }
        cur_node = go;
    }   
    trie[cur_node].is_word = true;
}

int go(int cur_node, char c);

int getSuffLink(int cur_node) {
    if (trie[cur_node].suff_link != -1)
        return trie[cur_node].suff_link;
    if (trie[cur_node].par == 0) 
        return trie[cur_node].suff_link = 0;
    char c = trie[cur_node].c;
    int parent = trie[cur_node].par;
    return trie[cur_node].suff_link = go(trie[parent].suff_link, c); 
}

int go(int cur_node, char c) {
    if (trie[cur_node].go.count(c) > 0)
        return trie[cur_node].go[c];
    if (cur_node == 0)
        return trie[cur_node].go[c] = 0;
    int suff_link = getSuffLink(cur_node);
    return trie[cur_node].go[c] = go(suff_link, c);
}

void buildAhoCorasick() {
    queue <int> q;
    q.push(0);
    while (!q.empty()) {
        int cur_node = q.front();
        q.pop();

        for (map <char, int> :: iterator it = trie[cur_node].go.begin(); it != trie[cur_node].go.end(); it++) {
            q.push(it->second);
        }

        int suff_link = getSuffLink(cur_node);
        trie[cur_node].suff_link = suff_link;
        if (trie[suff_link].is_word)
            trie[cur_node].is_word = true;
    }
}

int main() {
    assert(freopen("console.in","r",stdin));
    assert(freopen("console.out","w",stdout));

    node root;
    root.suff_link = 0;
    trie.push_back(root);

    scanf("%d", &n);
    gets(s);

    for (int i = 1; i <= n; i++) {
        gets(s);
        trieInsert(s);
    }

    buildAhoCorasick();

    while (gets(s)) {
        int cur_node = 0;
        int len = strlen(s);
        for (int i = 0; i < len; i++) {
            cur_node = go(cur_node, s[i]);
            if (trie[cur_node].is_word) {
                puts(s);
                break;
            }
        }
    }

    return 0;
}