题目链接：http://codeforces.com/contest/430/problem/c
题意：一棵树上的节点为0或1，希望把节点上的值变为目标值。选择几个点，这几个点会翻转，同时它的孙子…也会翻转，问最少需要修改几个节点。
任选一点开始DFS，判断某点翻转后是否与目标值相同，相同的话则不翻转，不相同则翻转，并且记录该点。
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("%I64d", &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 onecnt(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 = 100100; 72 int n; 73 int init[maxn], goal[maxn]; 74 bool vis[maxn]; 75 vector<int> edge[maxn]; 76 vector<int> ans; 77 78 void dfs(int u, int x, int y) { 79 if((init[u] ^ x) != goal[u]) { 80 ans.pb(u); 81 x = !x; 82 } 83 Rep(i, edge[u].size()) { 84 int v = edge[u][i]; 85 if(vis[v]) continue; 86 vis[v] = 1; 87 dfs(v, y, x); 88 } 89 } 90 91 int main() { 92 // FRead(); 93 int u, v; 94 Rint(n); 95 Rep(i, n-1) { 96 Rint(u); Rint(v); 97 edge[u].pb(v); 98 edge[v].pb(u); 99 } 100 For(i, 1, n+1) Rint(init[i]); 101 For(i, 1, n+1) Rint(goal[i]); 102 vis[1] = 1; 103 dfs(1, 0, 0); 104 printf("%d ", ans.size()); 105 Rep(i, ans.size()) printf("%d ", ans[i]); 106 RT 0; 107 }