题意：训练指南P250

分析：DFS记忆化搜索，范围或者说是图是已知的字串构成的自动机图，那么用 | (1 << i)表示包含第i个字串，如果长度为len，且st == (1 << m) - 1则是可能的。打印与之前相似。

#include 
     
      using namespace std;typedef long long ll;const int N = 25 + 5;const int NODE = 10 * 10 + 5;const int M = (1 << 10) + 5;const int SIZE = 26;int n, m;char str[12];struct AC   {    int ch[NODE][SIZE], val[NODE], fail[NODE], last[NODE], sz;    ll dp[NODE][N][M];  int out[N];    void clear(void)    {        memset (ch[0], 0, sizeof (ch[0]));        sz = 1;    }    int idx(char c) {        return c - 'a';    }    void insert(char *s, int v)   {        int u = 0;        for (int c, i=0; s[i]; ++i)    {            c = idx (s[i]);            if (!ch[u][c])  {                memset (ch[sz], 0, sizeof (ch[sz]));                val[sz] = 0;                ch[u][c] = sz++;            }            u = ch[u][c];        }        val[u] |= (1 << v);    }    void build(void) {        queue
      
        que; fail[0] = 0;        for (int c=0; c
       
         0)   {                out[len] = c;                print (ch[now][c], len + 1, st | val[ch[now][c]]);            }        }    }    ll DP(int now, int len, int st)   {        ll &ans = dp[now][len][st];        if (ans != -1) return ans;        if (len == n)   {            if (st == (1 << m) - 1) return ans = 1;            else    return ans = 0;        }        ans = 0;        for (int c=0; c