题意

题目链接

Sol

线性基是可以合并的

倍增维护一下

然后就做完了？？

喵喵喵？

// luogu-judger-enable-o2
#include<bits/stdc++.h>
#define LL long long
using namespace std;
const int MAXN = 2e4 + 10, B = 60;
inline LL read() {char c = getchar(); LL x = 0, f = 1;while(c < '0' || c > '9') {if(c == '-') f = -1; c = getchar();}while(c >= '0' && c <= '9') x = x * 10 + c - '0', c = getchar();return x * f;
}
int N, Q, g[MAXN][16], dep[MAXN];
LL a[MAXN];
vector<int> v[MAXN];
struct Node {LL P[62];Node() {memset(P, 0, sizeof(P));}void insert(LL x) {for(int i = B; i >= 0; i--) {if((!(x >> i & 1))) continue;if(P[i]) {x ^= P[i]; continue;}P[i] = x; break;}}LL QueryMax() {LL ans = 0;for(int i = B; i >= 0; i--) ans = max(ans, ans ^ P[i]);return ans;}Node operator + (const Node &rhs) const {Node ans; for(int i = 0; i <= B; i++) ans.P[i] = this -> P[i];for(int i = 0; i <= B; i++) if(rhs.P[i]) ans.insert(rhs.P[i]);return ans; }
}f[MAXN][16];
void dfs(int x, int fa) {dep[x] = dep[fa] + 1;g[x][0] = fa;f[x][0].insert(a[x]); f[x][0].insert(a[fa]);for(int i = 0; i < v[x].size(); i++) {int to = v[x][i];if(to == fa) continue;dfs(to, x);}
}
void Pre() {for(int j = 1; j <= 15; j++)for(int i = 1; i <= N; i++)g[i][j] = g[g[i][j - 1]][j - 1], f[i][j] = f[i][j - 1] + f[g[i][j - 1]][j - 1];
}
LL Query(int x, int y) {Node base; base.insert(a[x]); base.insert(a[y]);if(dep[x] < dep[y]) swap(x, y);for(int i = 15; i >= 0; i--)if(dep[g[x][i]] >= dep[y])base = base + f[x][i], x = g[x][i];if(x == y) return base.QueryMax();for(int i = 15; i >= 0; i--)if(g[x][i] != g[y][i]) {base = base + f[x][i];base = base + f[y][i];x = g[x][i], y = g[y][i];}base = base + f[x][0]; base = base + f[y][0];return base.QueryMax();
}
int main() {
#ifndef ONLINE_JUDGE//freopen("a.in", "r", stdin); freopen("b.out", "w", stdout);
#endifN = read(); Q = read();for(int i = 1; i <= N; i++) a[i] = read();for(int i = 1; i <= N - 1; i++) {int x = read(), y = read();v[x].push_back(y); v[y].push_back(x);}dfs(1, 0);Pre();while(Q--) {int x = read(), y = read();printf("%lld\n", Query(x, y));}return 0;
}
/*
8 4
45654 251 321 54687 321321 654 6321432 5646
1 2
2 3
2 4
1 5
4 6
6 7
5 87 8
7 5
6 8
4 1
*/