【UOJ #13】【UER #1】跳蚤OS

http://uoj.ac/problem/13

建立trie树，然后建立go指针，

和AC自动机里的fail指针差不多，

走到一个快捷方式就从go指针走。

注意在trie树上要保留字符'/'，不能用end标记来标识一个字符串的结束。

因为可能出现"/Iam/zz"和"/Iamzz"这两种情况，如果只用end标记，tire树上这两个字符串就会共用一条路径。

(总之是蒟蒻才会犯的错误，神犇们勿喷_(:з」∠)_)

#include<cstdio>
#include<cstring>
#include<algorithm>
using namespace std;
typedef long long ll;
int in() {
	int k = 0; char c = getchar();
	for(; c < '0' || c > '9'; c = getchar());
	for(; c >= '0' && c <= '9'; c = getchar())
		k = k * 10 + c - 48;
	return k;
}

struct State {
	int num;
	State *nxt[27], *go, *fa;
	State(State *_fa, int _num) {
		memset(nxt, 0, sizeof(nxt));
		go = 0; fa = _fa; num = _num;
	}
} *root;

State *to(char *c) {
	int len = strlen(c), x;
	if (len == 1 && c[0] == '/') return root;
	State *tmp = root;
	for(int i = 0; i < len; ++i) {
		if (c[i] == '/') x = 26;
		else x = c[i] - 'a';
		if (tmp->nxt[x] == 0)
			tmp->nxt[x] = new State(tmp, x);
		tmp = tmp->nxt[x];
		if ((c[i + 1] == '\0' || c[i + 1] == '/') && tmp->go)
			tmp = tmp->go;
	}
	return tmp;
}

char s[500003], t[500003];

void print(State *tmp) {
	int tot = 0;
	if (tmp == root) {puts("/"); return;}
	while (tmp != root) {
		if (tmp->num <= 25) t[++tot] = 'a' + tmp->num;
		else t[++tot] = '/';
		tmp = tmp->fa;
	}
	while (tot) putchar(t[tot--]);
	puts("");
}

int n, m;

int main() {
	root = new State(0, 0);
	n = in(); m = in();
	for(int i = 1; i <= n; ++i) {
		scanf("%s", s); scanf("%s", t);
		to(s)->go = to(t);
	}
	for(int i = 1; i <= m; ++i) {
		scanf("%s", s);
		print(to(s));
	}
	return 0;
}