P5231 [JSOI2012]玄武密码（AC自动机）

[JSOI2012]玄武密码

AC自动机经典题。

建好AC机后我们只需求出每个点是不是母串的子串即可。

和统计是一样的道理，如果点x是母串的子串那么fail[x]也是。

然后对于每个串只需暴力网上跳到根判断即可。

#include <bits/stdc++.h>
using namespace std;
const int N = 10000010;
const int M = 100010;
const int Sigma = 4;
namespace StandardIO{
	template <typename T> void read(T &x) {
		int f = 1;
		char ch = getchar();
		for (; !isdigit(ch); ch = getchar()) if (ch == '-') f = -1;
		for (; isdigit(ch); ch = getchar()) x = x * 10 + ch - '0';
		x *= f;
	}
	template <typename T> void write(T x) {
		if (x > 9) write(x / 10);
		putchar(x % 10 + '0');
	}
	template <typename T> void print(T x) {
		if (x < 0) putchar('-'), x = -x;
		write(x);
		putchar('
');
	}
}using namespace StandardIO;
int n, m;
char s[N], t[110];
namespace ACAM{
	int trie[N][4], fail[N], fa[N], in[N], tot = 1;
	int End[M], Len[M];
	bool mark[N];
	inline int f(char c) {
		switch (c) {
			case 'E':
				return 0;
			case 'S':
				return 1;
			case 'W':
				return 2;
			case 'N':
				return 3;
			default:
				puts("Wrong");
				return -1;
		}
	}
	inline void insert(int id) {
		int T = strlen(t + 1), p = 1;
		for (int i = 1; i <= T; i++) {
			int k = f(t[i]);
			if (!trie[p][k]) trie[p][k] = ++tot, fa[trie[p][k]] = p;
			p = trie[p][k];
		}
		End[id] = p;
		Len[id] = T;
	}
	inline void get_fail() {
		queue<int> q;
		while (!q.empty()) q.pop();
		for (int i = 0; i < Sigma; i++)
			trie[0][i] = 1;
		fail[1] = 0;
		q.push(1);
		while (!q.empty()) {
			int x = q.front();
			q.pop();
			for (int i = 0; i < Sigma; i++) {
				if (trie[x][i])
					fail[trie[x][i]] = trie[fail[x]][i], q.push(trie[x][i]);
				else
					trie[x][i] = trie[fail[x]][i];
			}
		}
	}
	inline void work() {
		int p = 1;
		for (int i = 1; i <= n; i++) {
			int k = f(s[i]);
			p = trie[p][k];
			mark[p] = true;
		}
		queue<int> q;
		while (!q.empty()) q.pop();
		for (int i = 1; i <= tot; i++) in[fail[i]]++;
		for (int i = 1; i <= tot; i++) if (in[i] == 0) q.push(i);
		while (!q.empty()) {
			int x = q.front();
			q.pop();
			mark[fail[x]] |= mark[x];
			in[fail[x]]--;
			if (in[fail[x]] == 0) q.push(fail[x]);
		}
	}
}using namespace ACAM;

int main() {
	read(n); read(m);
	scanf("%s", s + 1);
	for (int i = 1; i <= m; ++i) {
		scanf("%s", t + 1);
		insert(i);
	}
	get_fail();
	work();
	for (int i = 1; i <= m; ++i) {
		int p = End[i];
		while (p) {
			if (mark[p]) {
				break;
			}
			Len[i]--;
			p = fa[p];
		}
		print(Len[i]);
	}
	return 0;
}