题目传送门
1 /*
2 题意：两块扑克牌按照顺序叠起来后，把下半部分给第一块，上半部给第二块，一直持续下去，直到叠成指定的样子
3 DFS：直接模拟搜索，用map记录该字符串是否被搜过。读懂题目是关键。
4 */
5 /************************************************
6 Author :Running_Time
7 Created Time :2015-8-3 13:57:55
8 File Name :POJ_3087.cpp
9 *************************************************/
10
11 #include <cstdio>
12 #include <algorithm>
13 #include <iostream>
14 #include <sstream>
15 #include <cstring>
16 #include <cmath>
17 #include <string>
18 #include <vector>
19 #include <queue>
20 #include <deque>
21 #include <stack>
22 #include <list>
23 #include <map>
24 #include <set>
25 #include <bitset>
26 #include <cstdlib>
27 #include <ctime>
28 using namespace std;
29
30 #define lson l, mid, rt << 1
31 #define rson mid + 1, r, rt << 1 | 1
32 typedef long long ll;
33 const int MAXN = 5e3 + 10;
34 const int INF = 0x3f3f3f3f;
35 const int MOD = 1e9 + 7;
36 map<string, int> cnt;
37 string str;
38 bool vis[MAXN][MAXN];
39 int res, ct;
40 int n;
41
42 void DFS(string s, string t, int dep) {
43 if (!cnt.count (s)) cnt[s] = ++ct;
44 if (!cnt.count (t)) cnt[t] = ++ct;
45 if (vis[cnt[s]][cnt[t]]) return ;
46 vis[cnt[s]][cnt[t]] = true;
47 string tmp = "";
48 for (int i=0; i<n; ++i) {
49 tmp += t[i]; tmp += s[i];
50 }
51 if (tmp == str) {
52 if (res > dep) res = dep;
53 return ;
54 }
55 s = ""; t = "";
56 for (int i=0; i<n; ++i) s += tmp[i];
57 for (int i=n; i<2*n; ++i) t += tmp[i];
58 DFS (s, t, dep + 1);
59 }
60
61 int main(void) { //POJ 3087 Shuffle'm Up
62 int T, cas = 0; scanf ("%d", &T);
63 while (T--) {
64 scanf ("%d", &n);
65 string s, t;
66 cin >> s >> t; cin >> str;
67 res = INF; ct = 0; cnt.clear (); memset (vis, false, sizeof (vis));
68 DFS (s, t, 1);
69 printf ("%d %d
", ++cas, res == INF ? -1 : res);
70 }
71
72 return 0;
73 }