CUBE-186: XOR tree

#include <bits/stdc++.h>
using namespace std;

using pii = pair<int,int>;
vector <pii> g[100001];
int XOR[100001];
bool visited[100001];

int main(){

    int n,m;
    scanf("%d%d",&n,&m);

    for(int i=1;i<=n-1;i++){
        int u,v,w;
        scanf("%d%d%d",&u,&v,&w);
        g[u].push_back({v,w});
        g[v].push_back({u,w});
    }

    queue <pii> q;
    q.push({1,0});
    XOR[1] = 0;

    while(q.size() > 0){
        int u,d;
        u = q.front().first;
        d = q.front().second;
        q.pop();

        if(visited[u]) continue;
        visited[u] = true;

        for(auto vw:g[u]){
            int v,w;
            v = vw.first;
            w = vw.second;
            if(!visited[v]){
                XOR[v] = w^d;
                q.push({v,w^d});
            }
        }
    }

    for(int i=1;i<=m;i++){
        int u,v;
        scanf("%d%d",&u,&v);
        printf("%d\n",XOR[u]^XOR[v]);
    }

    return 0;
}