lca倍增的途中，merge一下线性基。注意线性基是从自己开始，而倍增数组fa[i][0]等于father，意味着，线性基倍增的区间是左闭右开的，fa数组是左闭右闭
#include<iostream>
#include<cstring>
#include<algorithm>
#include<cmath>
#include<cstdlib>
#include<climits>
#include<stack>
#include<vector>
#include<queue>
#include<set>
#include<bitset>
#include<map>
//#include<regex>
#include<cstdio>
#include <iomanip>
#pragma GCC optimize(2)
#define up(i,a,b) for(ll i=a;i<b;i++)
#define dw(i,a,b) for(ll i=a;i>b;i--)
#define upd(i,a,b) for(ll i=a;i<=b;i++)
#define dwd(i,a,b) for(ll i=a;i>=b;i--)
//#define local
typedef long long ll;
typedef unsigned long long ull;
const double esp = 1e-6;
const double pi = acos(-1.0);
const int INF = 0x3f3f3f3f;
const int inf = 1e9;
using namespace std;
ll read()
{
char ch = getchar(); ll x = 0, f = 1;
while (ch<‘0‘ || ch>‘9‘) { if (ch == ‘-‘)f = -1; ch = getchar(); }
while (ch >= ‘0‘ && ch <= ‘9‘) { x = x * 10 + ch - ‘0‘; ch = getchar(); }
return x * f;
}
typedef pair<int, int> pir;
#define lson l,mid,root<<1
#define rson mid+1,r,root<<1|1
#define lrt root<<1
#define rrt root<<1|1
const int N = 20010;
struct node {
int next, to;
}edge[N*2];
int head[N];
int cnt = 0;
void addedge(int u, int v)
{
edge[cnt].next = head[u];
edge[cnt].to = v;
head[u] = cnt++;
}
ll val[N];
int n, q;
int dep[N];
int f[N][30];
struct xxj {
ll b[65];
xxj() {
upd(i, 0, 60)b[i] = 0;
}
void insert(ll x)
{
dwd(i, 60, 0)
{
if (x >> i & 1ll)
{
if (b[i])
{
x ^= b[i];
}
else {
b[i] = x;
upd(j, 0, i - 1)if (b[i] >> j & 1ll)b[i] ^= b[j];
upd(j, i + 1, 60)if (b[j] >> i & 1ll)b[j] ^= b[i];
break;
}
}
}
}
}X[N][21];
void merge(xxj &t1, xxj t2)
{
dwd(i, 60, 0)
{
if (t2.b[i] == 0)continue;
t1.insert(t2.b[i]);
}
}
void dfs(int u, int fa)
{
dep[u] = dep[fa] + 1;
f[u][0] = fa;
X[u][0].insert(val[u]);
upd(i, 1, 20)
{
if (f[u][i - 1] == 0)break;
f[u][i] = f[f[u][i - 1]][i - 1];
merge(X[u][i], X[f[u][i - 1]][i - 1]);
merge(X[u][i], X[u][i - 1]);
}
for (int i = head[u]; ~i; i = edge[i].next)
{
int v = edge[i].to;
if (v == fa)continue;
dfs(v, u);
}
}
xxj lca(int x, int y)
{
if (dep[x] < dep[y])swap(x, y);
xxj temp;
if (dep[x] != dep[y])
{
dwd(i, 20, 0)
{
if (dep[f[x][i]] < dep[y])continue;
merge(temp, X[x][i]);
x = f[x][i];
}
}
if (x == y)
{
temp.insert(val[x]);
return temp;
}
dwd(i, 20, 0)
{
if (f[x][i] != f[y][i])
{
merge(temp, X[x][i]);
merge(temp, X[y][i]);
x = f[x][i]; y = f[y][i];
}
}
temp.insert(val[f[x][0]]);
temp.insert(val[x]);
temp.insert(val[y]);
return temp;
}
int main()
{
n = read(), q = read();
memset(head, -1, sizeof(head));
upd(i, 1, n)val[i] = read();
ll u, v;
upd(i, 1, n - 1)
{
u = read(), v = read();
addedge(u, v); addedge(v, u);
}
dfs(1, 0);
while (q--)
{
u = read(), v = read();
xxj res = lca(u, v);
ll ans = 0;
dwd(i, 60, 0)
{
ans ^= res.b[i];
}
printf("%lld\n", ans);
}
return 0;
}
原文：https://www.cnblogs.com/LORDXX/p/13263556.html