【Uva11468】Substring【AC自动机】【概率DP】

http://acm.hust.edu.cn/vjudge/problem/viewProblem.action?id=31655

大白上的题。

AC自动机经典题型。

论如何忘记写getfail()。

/* Footprints In The Blood Soaked Snow */
#include <cstdio>
#include <cstring>
#include <algorithm>

using namespace std;

typedef double DB;

const int maxnode = 405, maxn = 105, maxl = 105, M = 61, maxq = 10000;
const DB eps = 1e-9;

int q[maxq];
DB pro[maxn], dp[maxnode][maxl];
bool vis[maxnode][maxl];

inline int getid(char ch) {
	if(ch >= 'a' && ch <= 'z') return ch - 'a';
	if(ch >= 'A' && ch <= 'Z') return ch - 'A' + 26;
	if(ch >= '0' && ch <= '9') return ch - '0' + 52;
}

struct _acm {
	int son[maxnode][maxn], acmcnt, fail[maxnode];
	bool flag[maxnode];

	void init() {
		memset(son, 0, sizeof(son)); acmcnt = 0;
		for(int i = 0; i < maxnode; i++) fail[i] = flag[i] = 0;
	}

	void insert(char *s) {
		int now = 0, len = strlen(s);
		for(int i = 0; i < len; i++) {
			int &pos = son[now][getid(s[i])];
			if(!pos) pos = ++acmcnt;
			now = pos;
		}
		flag[now] = 1;
	}

	void getfail() {
		int h = 0, t = 0;
		for(int i = 0; i <= M; i++) if(son[0][i]) q[t++] = son[0][i];
		while(h != t) {
			int u = q[h++];
			for(int i = 0; i <= M; i++)
				if(!son[u][i]) son[u][i] = son[fail[u]][i];
				else {
					fail[q[t++] = son[u][i]] = son[fail[u]][i];
					flag[son[u][i]] |= flag[fail[son[u][i]]];
				}
		}
	}

	DB dfs(int u, int L) {
		if(!L) return 1.0;
		if(vis[u][L]) return dp[u][L];
		vis[u][L] = 1; dp[u][L] = 0.0;
		for(int i = 0; i <= M; i++)
			if(!flag[son[u][i]]) dp[u][L] += pro[i] * dfs(son[u][i], L - 1);
		return dp[u][L];
	}
} acm;

char str[maxn];

int main() {
	int T; scanf("%d", &T);
	for(int cas = 1; cas <= T; cas++) {
		acm.init();
		memset(vis, 0, sizeof(vis));
		for(int i = 0; i <= M; i++) pro[i] = 0.0;

		int m; scanf("%d", &m);
		for(int i = 1; i <= m; i++) {
			scanf("%s", str);
			acm.insert(str);
		}
		acm.getfail();

		scanf("%d", &m);
		for(int i = 1; i <= m; i++) {
			DB x;
			scanf("%s%lf", str, &x);
			pro[getid(str[0])] = x;
		}

		scanf("%d", &m);
		printf("Case #%d: %.6lf\n", cas, acm.dfs(0, m));
	}
	return 0;
}