[题解]LuoGu2420：让我们异或吧

原题传送门
树剖裸题~~
查询两点路径异或和
不同之处是此题为边权，采用以点代边的方式，用一条边两端点中深度更大的那个点代表这条边

当然，这道题也可以用树上倍增做，非常水的一道题，不过树剖练手也是不错哒

Code：

#include <bits/stdc++.h>
#define maxn 100010
#define ls rt << 1
#define rs rt << 1 | 1
using namespace std;
struct Edge{
    int to, next;
}edge[maxn << 1];
struct Line{
    int x, y, z;
}line[maxn];
struct Seg{
    int l, r, sum;
}seg[maxn << 2];
int head[maxn], num, d[maxn], fa[maxn], size[maxn], son[maxn];
int id[maxn], cnt, w[maxn], wt[maxn], top[maxn];
int n;

inline int read(){
    int s = 0, w = 1;
    char c = getchar();
    for (; !isdigit(c); c = getchar()) if (c == '-') w = -1;
    for (; isdigit(c); c = getchar()) s = (s << 1) + (s << 3) + (c ^ 48);
    return s * w;
}

void add_edge(int x, int y){ edge[++num].to = y; edge[num].next = head[x]; head[x] = num; }

void dfs(int u){
    size[u] = 1, son[u] = -1;
    for (int i = head[u]; i; i = edge[i].next){
        int v = edge[i].to;
        if (v != fa[u]){
            fa[v] = u, d[v] = d[u] + 1;
            dfs(v);
            size[u] += size[v];
            if (son[u] == -1 || son[u] != -1 && size[son[u]] < size[v]) son[u] = v;
        }
    }
}

void dfs(int u, int x){
    id[u] = ++cnt, top[u] = x, wt[cnt] = w[u];
    if (son[u] == -1) return;
    dfs(son[u], x);
    for (int i = head[u]; i; i = edge[i].next){
        int v = edge[i].to;
        if (v != fa[u] && v != son[u]) dfs(v, v);
    }
}

void pushup(int rt){ seg[rt].sum = seg[ls].sum ^ seg[rs].sum; }

void build(int rt, int l, int r){
    seg[rt].l = l, seg[rt].r = r;
    if (l == r){
        seg[rt].sum = wt[l]; return;
    }
    int mid = (l + r) >> 1;
    build(ls, l, mid); build(rs, mid + 1, r);
    pushup(rt);
}

int query(int rt, int l, int r){
    if (seg[rt].l > r || seg[rt].r < l) return 0;
    if (seg[rt].l >= l && seg[rt].r <= r) return seg[rt].sum;
    return query(ls, l, r) ^ query(rs, l, r);
}

int main(){
    n = read();
    for (int i = 1; i < n; ++i){
        int x = read(), y = read(), z = read();
        add_edge(x, y); add_edge(y, x);
        line[i].x = x, line[i].y = y, line[i].z = z;
    }
    dfs(1); 
    for (int i = 1; i < n; ++i) w[fa[line[i].x] == line[i].y ? line[i].x : line[i].y] = line[i].z;
    dfs(1, 1);
    build(1, 1, n);
    int m = read();
    while (m--){
        int x = read(), y = read();
        int ans = 0;
        while (top[x] != top[y]){
            if (d[top[x]] < d[top[y]]) swap(x, y);
            ans ^= query(1, id[top[x]], id[x]);
            x = fa[top[x]];
        }
        if (d[x] < d[y]) swap(x, y);
        ans ^= query(1, id[y] + 1, id[x]);
        printf("%d\n", ans);
    }
    return 0;
}