[Luogu] 让我们异或吧

https://www.luogu.org/problemnew/show/P2420

异或满足

A ^ B = B ^ A

A ^ A = 0

0 ^ A = A

#include <cstdio>
#include <iostream>

using namespace std;
const int N = 1e5 + ;

#define yxy getchar()

#define RR freopen("gg.in", "r", stdin)

int n, Ty, now = , head[N], A[N];
struct Node{int u, v, w, nxt;} G[N << ];

inline int read() {
    int x = , f = ; char c = yxy;
    while(c < '' || c > '') {if(c == '-') f = -; c = yxy;}
    while(c >= '' && c <= '') x = x *  + c - '', c = yxy;
    return x * f;
}

void Add(int u, int v, int w) {
    G[now].v = v; G[now].w = w; G[now].nxt = head[u]; head[u] = now ++;
}

void Dfs(int u, int fa) {
    for(int i = head[u]; ~ i; i = G[i].nxt) {
        int v = G[i].v;
        if(v != fa) {
            A[v] = G[i].w ^ A[u];
            Dfs(v, u);
        }
    }
}

int main() {
    n = read();
    for(int i = ; i <= n; i ++) head[i] = -;
    for(int i = ; i < n; i ++) {
        int u = read(), v = read(), w = read();
        Add(u, v, w); Add(v, u, w);
    }
    Dfs(, );
    Ty = read();
    while(Ty --) {
        int u = read(), v = read();
        cout << (A[u] ^ A[v]) << endl;
    }

    return  ;
}