【BZOJ1030】[JSOI2007]文本生成器【AC自动机】【计数DP】

http://www.lydsy.com/JudgeOnline/problem.php?id=1030

AC自动机经典题型，数据不大，不用矩阵快速幂优化。

/* Footprints In The Blood Soaked Snow */
#include <cstdio>
#include <cstring>
#define cls(a, x) memset(a, x, sizeof(a))

using namespace std;

const int maxn = 6005, maxm = 105, p = 10007, maxq = 10000;

int dp[maxm][maxn], q[maxq];

struct _acm {
	int son[maxn][26], fail[maxn], acmcnt;
	bool flag[maxn];

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

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

	void getfail() {
		int h = 0, t = 0;
		for(int i = 0; i < 26; i++) if(son[0][i]) q[t++] = son[0][i];
		while(h != t) {
			int u = q[h++];
			for(int i = 0; i < 26; 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]]];
				}
		}
	}
} acm;

inline int qpow(int a, int n) {
	int ans = 1;
	for(int t = a; n; n >>= 1, t = t * t % p) if(n & 1) ans = ans * t % p;
	return ans;
}

char str[maxm];

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

	dp[0][0] = 1;
	for(int i = 1; i <= m; i++) for(int j = 0; j <= acm.acmcnt; j++) for(int k = 0; k < 26; k++)
		if(!acm.flag[acm.son[j][k]]) dp[i][acm.son[j][k]] = (dp[i][acm.son[j][k]] + dp[i - 1][j]) % p;

	int ans = qpow(26, m);
	for(int i = 0; i <= acm.acmcnt; i++) ans = (ans - dp[m][i] + p) % p;
	printf("%d\n", ans);
	return 0;
}