DP(记忆化搜索) + AC自动机 LA 4126 Password Suspects

 

题目传送门

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 <bits/stdc++.h>
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<int> que; fail[0] = 0;
        for (int c=0; c<SIZE; ++c)  {
            int u = ch[0][c];
            if (u)  {
                fail[u] = 0;    last[u] = 0;
                que.push (u);
            }
        }
        while (!que.empty ())   {
            int r = que.front ();   que.pop ();
            for (int c=0; c<SIZE; ++c)  {
                int &u = ch[r][c];
                if (!u) {
                    u = ch[fail[r]][c]; continue;
                }
                que.push (u);
                int v = fail[r];
                while (v && !ch[v][c])  v = fail[v];
                fail[u] = ch[v][c];
                val[u] |= val[fail[u]];
                //last[u] = val[fail[u]] ? fail[u] : last[fail[u]];
            }
        }
    }
    void print(int now, int len, int st)    {
        if (len == n)   {
            for (int i=0; i<len; ++i)   {
                printf ("%c", out[i] + 'a');
            }
            puts ("");  return ;
        }
        for (int c=0; c<SIZE; ++c)  {
            if (dp[ch[now][c]][len+1][st|val[ch[now][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<SIZE; ++c)  {
            ans += DP (ch[now][c], len + 1, st | val[ch[now][c]]);
        }
        return ans;
    }
    void run(void)  {
        memset (dp, -1, sizeof (dp));
        ll ans = DP (0, 0, 0);
        printf ("%lld suspects\n", ans);
        if (ans <= 42)  {
            print (0, 0, 0);
        }
    }
}ac;

int main(void)  {
    int cas = 0;
    while (scanf ("%d%d", &n, &m) == 2) {
        if (!n && !m)   break;
        ac.clear ();
        for (int i=0; i<m; ++i) {
            scanf ("%s", &str);
            ac.insert (str, i);
        }
        ac.build ();
        printf ("Case %d: ", ++cas);
        ac.run ();
    }

    return 0;
}