NC20857 Xor Path(树形DP)

题目链接

题意：



题解：

AC代码

/*
    Author : zzugzx
    Lang : C++
    Blog : blog.csdn.net/qq_43756519
*/
#include<bits/stdc++.h>
using namespace std;

#define fi first
#define se second
#define pb push_back
#define mp make_pair
#define all(x) (x).begin(), (x).end()
#define endl '\n'
#define SZ(x) (int)x.size()
#define mem(a, b) memset(a, b, sizeof(a))

typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
//const int mod = 1e9 + 7;
const int mod = 998244353;

const double eps = 1e-6;
const double pi = acos(-1.0);
const int maxn = 1e6 + 10;
const int N = 410;
const ll inf = 0x3f3f3f3f;
const int dir[][2]={{0, 1}, {1, 0}, {0, -1}, {-1, 0}, {1, 1}, {1, -1}, {-1, 1}, {-1, -1}};
ll a[maxn], sz[maxn], ans, n;
vector<int> g[maxn];
void dfs(int u, int fa) {
    sz[u] = 1;
    ll res = 0;
    for (auto v : g[u]) {
        if (v == fa) continue;
        dfs(v, u);
        res = (res + (sz[u] - 1) * sz[v]) % 2;
        sz[u] += sz[v];
    }
    res = (res + (sz[u] - 1) * (n - sz[u]) + n + 1) % 2;
    if (res & 1) ans ^= a[u];
}
int main()
{
    ios::sync_with_stdio(false);
    cin.tie(0); cout.tie(0);
  //freopen("in.txt", "r", stdin);
  //freopen("out.txt", "w", stdout);
    cin >> n;
    for (int i = 1; i < n; i++) {
        int u, v;
        cin >> u >> v;
        g[u].pb(v);
        g[v].pb(u);
    }
    for (int i = 1; i <= n; i++)
        cin >> a[i];
    dfs(1, 0);
    cout << ans << endl;
    return 0;
}