WHU1572 Cyy and Fzz (AC自动机 dp )

#include <iostream>
#include <queue>
#include <cstdio>
#include <string>
#include <cstring>
using namespace std;
const int SD = 26;
const int MAXL = 1000;
struct Tire {
    int next[MAXL][SD], fail[MAXL], eofs[MAXL];
    int Root, cnt;
    int newnode() {
        for (int i = 0; i < SD; i++)     next[cnt][i] = -1;
        eofs[cnt++] = 0;
        return cnt - 1;
    }
    void init() {
        cnt = 0;
        Root = newnode();
    }
    void Ins (char buf[], int k) {
        int len = strlen (buf);
        int now = Root;
        for (int i = 0; i < len; i++) {
            if (next[now][buf[i] - ‘a‘] == -1)
                next[now][buf[i] - ‘a‘] = newnode();
            now = next[now][buf[i] - ‘a‘];
        }
        eofs[now] |= (1 << k);
    }
    void build() {
        queue<int> ql;
        fail[Root] = Root;
        for (int i = 0; i < SD; i++) {
            if (next[Root][i] == -1)
                next[Root][i] = Root;
            else {
                fail[next[Root][i]] = Root;
                ql.push (next[Root][i]);
            }
        }
        while (!ql.empty() ) {
            int now = ql.front(); ql.pop();
            eofs[now] |= eofs[fail[now]];
            for (int i = 0; i < SD; i++)
                if (next[now][i] == -1) {
                    next[now][i] = next[fail[now]][i];
                }
                else {
                    fail[next[now][i]] = next[fail[now]][i];
                    ql.push (next[now][i]);
                }
        }
    }
} AC;
int Cs, n, m;
char s[20];
double dp[20][400][1 << 9], tmp = 1. / 26;
int main() {
    scanf ("%d", &Cs);
    while (Cs--) {
        memset (dp, 0, sizeof dp);
        AC.init();
        scanf ("%d %d", &n, &m);
        for (int i = 0; i < n; i++) {
            scanf ("%s", s);
            AC.Ins (s, i);
        }
        AC.build();

        dp[0][0][0] = 1;
        for (int i = 0; i < m; i++)
            for (int u = 0; u < AC.cnt; u++)
                for (int st = 0; st < (1 << n); st++)
                    if (dp[i][u][st] > 0)
                        for (int j = 0; j < SD; j++) {
                            int v = AC.next[u][j];
                            dp[i + 1][v][st | AC.eofs[v]] += dp[i][u][st] * tmp;
                        }

        double ans = 0;
        for (int i = 0; i < AC.cnt; i++)
            for (int st = 0; st < (1 << n); st++)
                if (dp[m][i][st] > 0) {
                    int sum = 0;
                    for (int k = 0; k < n; k++)
                        if (st & (1 << k) ) sum++;
                    ans += dp[m][i][st] * sum;
                }
        printf ("%.6f\n", ans);
    }
}