Xor tree

#include<stdio.h>
#include<vector>
#include<queue>
using namespace std;
typedef long long int ll;
int main()
{
    int n,m;
    scanf("%d %d",&n,&m);
    vector<pair<ll,int> > adj[n+1];
    for(int i = 1 ; i < n ; i ++){
        int u,v;
        ll w;
        scanf("%d %d %lld",&u,&v,&w);
        adj[u].push_back({w,v});
        adj[v].push_back({w,u});
    }
    ll qxor[n+1];
    bool visited[n+1];
    for(int i = 1 ; i <= n ; i ++ ){
        visited[i] = false;
    }
    queue<int> q;
    qxor[1] = 0;
    q.push(1);
    while(!q.empty()){
        int u = q.front();
        q.pop();
        if(visited[u])continue;
        visited[u] = true;
        for(int i = 0 ; i <adj[u].size() ; i ++){
            int v = adj[u][i].second;
            ll w = adj[u][i].first;
            if(!visited[v]){
                qxor[v] = qxor[u] xor w;
                q.push(v);
            }
        }
    }
    for(int i = 0 ; i < m ; i ++){
        int u,v;
        scanf("%d %d",&u,&v);
        printf("%lld\n",qxor[u] xor qxor[v]);
    }
    return 0;
}