题目链接：http://hihocoder.com/problemset/problem/1041
学会了用C++的bitset哈，可喜可贺。以后遇到超过64位想用位来表示状态就不愁了哈。
这题用bitset存从节点1出发开始dfs，某点按照dfs顺序能够到达的所有点的集合。后序更新这个bitset，用或运算把下属的可达节点都更新上来。
先一遍dfs把bitset更新出来，再一遍dfs判断题中所给顺序是否合法。第二遍dfs的时候就按照给定的顺序扫描，根据某一个分支是不是有目标节点来判断退出。
1 /* 2 ━━━━━┒ギリギリ♂ eye！ 3 ┓┏┓┏┓┃キリキリ♂ mind！ 4 ┛┗┛┗┛┃＼○／ 5 ┓┏┓┏┓┃ / 6 ┛┗┛┗┛┃ノ) 7 ┓┏┓┏┓┃ 8 ┛┗┛┗┛┃ 9 ┓┏┓┏┓┃ 10 ┛┗┛┗┛┃ 11 ┓┏┓┏┓┃ 12 ┛┗┛┗┛┃ 13 ┓┏┓┏┓┃ 14 ┃┃┃┃┃┃ 15 ┻┻┻┻┻┻ 16 */ 17 #include <algorithm> 18 #include <iostream> 19 #include <iomanip> 20 #include <cstring> 21 #include <climits> 22 #include <complex> 23 #include <fstream> 24 #include <cassert> 25 #include <cstdio> 26 #include <bitset> 27 #include <vector> 28 #include <deque> 29 #include <queue> 30 #include <stack> 31 #include <ctime> 32 #include <set> 33 #include <map> 34 #include <cmath> 35 using namespace std; 36 #define fr first 37 #define sc second 38 #define cl clear 39 #define BUG puts("here!!!") 40 #define W(a) while(a--) 41 #define pb(a) push_back(a) 42 #define Rint(a) scanf("%d", &a) 43 #define Rll(a) scanf("%lld", &a) 44 #define Rs(a) scanf("%s", a) 45 #define Cin(a) cin >> a 46 #define FRead() freopen("in", "r", stdin) 47 #define FWrite() freopen("out", "w", stdout) 48 #define Rep(i, len) for(int i = 0; i < (len); i++) 49 #define For(i, a, len) for(int i = (a); i < (len); i++) 50 #define Cls(a) memset((a), 0, sizeof(a)) 51 #define Clr(a, x) memset((a), (x), sizeof(a)) 52 #define Full(a) memset((a), 0x7f7f7f, sizeof(a)) 53 #define lrt rt << 1 54 #define rrt rt << 1 | 1 55 #define pi 3.14159265359 56 #define RT return 57 #define lowbit(x) x & (-x) 58 #define onenum(x) __builtin_popcount(x) 59 typedef long long LL; 60 typedef long double LD; 61 typedef unsigned long long ULL; 62 typedef pair<int, int> pii; 63 typedef pair<string, int> psi; 64 typedef pair<LL, LL> pll; 65 typedef map<string, int> msi; 66 typedef vector<int> vi; 67 typedef vector<LL> vl; 68 typedef vector<vl> vvl; 69 typedef vector<bool> vb; 70 71 const int maxn = 110; 72 bitset<maxn> son[maxn]; 73 int n, m, cur; 74 int pos[maxn]; 75 bool vis[maxn]; 76 vi edge[maxn]; 77 bool flag; 78 79 void dfs1(int u, int p) { 80 son[u][u] = 1; vis[u] = 1; 81 Rep(i, edge[u].size()) { 82 int v = edge[u][i]; 83 if(!vis[v] && p != v) { 84 dfs1(v, u); 85 son[u] |= son[v]; 86 } 87 } 88 } 89 90 void dfs2(int u, int p) { 91 if(flag) return; 92 if(u == pos[cur]) cur++; 93 if(cur > m) { 94 flag = 1; 95 return; 96 } 97 vis[u] = 1; 98 while(cur <= m) { 99 int tmp = cur; 100 Rep(i, edge[u].size()) { 101 int v = edge[u][i]; 102 if(p != v && son[v][pos[cur]] && !vis[v]) { 103 dfs2(v, u); 104 } 105 } 106 if(tmp == cur) break; 107 } 108 } 109 110 int main() { 111 // FRead(); 112 int T, u, v; 113 Rint(T); 114 W(T) { 115 Rep(i, n+5) { 116 edge[i].cl(); 117 son[i].reset(); 118 } 119 Cls(vis); flag = 0; cur = 1; 120 Rint(n); 121 Rep(i, n-1) { 122 Rint(u); Rint(v); 123 edge[u].pb(v); 124 edge[v].pb(u); 125 } 126 Rint(m); 127 For(i, 1, m+1) Rint(pos[i]); 128 dfs1(1, -1); 129 Cls(vis); 130 dfs2(1, -1); 131 printf("%s ", flag ? "YES" : "NO"); 132 } 133 RT 0; 134 }