Count on a tree II [树分块]

bzoj2589
大概是选几个关键点，然后跳来跳去就好了。
b[40][40] 表示一条链上跳的QwQ

// powered by c++11
// by Isaunoya
#include <bits/stdc++.h>
#define rep(i, x, y) for (register int i = (x); i <= (y); ++i)
#define Rep(i, x, y) for (register int i = (x); i >= (y); --i)
using namespace std;
using db = double;
using ll = long long;
using uint = unsigned int;
#define Tp template
using pii = pair<int, int>;
#define fir first
#define sec second
Tp<class T> void cmax(T& x, const T& y) {
  if (x < y) x = y;
}
Tp<class T> void cmin(T& x, const T& y) {
  if (x > y) x = y;
}
#define all(v) v.begin(), v.end()
#define sz(v) ((int)v.size())
#define pb emplace_back
Tp<class T> void sort(vector<T>& v) { sort(all(v)); }
Tp<class T> void reverse(vector<T>& v) { reverse(all(v)); }
Tp<class T> void unique(vector<T>& v) { sort(all(v)), v.erase(unique(all(v)), v.end()); }
const int SZ = 1 << 23 | 233;
struct FILEIN {
  char qwq[SZ], *S = qwq, *T = qwq, ch;
#ifdef __WIN64
#define GETC getchar
#else
  char GETC() { return (S == T) && (T = (S = qwq) + fread(qwq, 1, SZ, stdin), S == T) ? EOF : *S++; }
#endif
  Tp<class T> void read(T& x) {
    bool sign = 0;
    while ((ch = GETC()) < 48) sign ^= (ch == 45);
    x = (ch ^ 48);
    while ((ch = GETC()) > 47) x = (x << 1) + (x << 3) + (ch ^ 48);
    x = sign ? -x : x;
  }
  FILEIN& operator>>(int& x) { return read(x), *this; }
} in;
struct FILEOUT {
  const static int LIMIT = 1 << 22;
  char quq[SZ], ST[233];
  int sz, O;
  ~FILEOUT() { flush(); }
  void flush() {
    fwrite(quq, 1, O, stdout);
    fflush(stdout);
    O = 0;
  }
  FILEOUT& operator<<(char c) { return quq[O++] = c, *this; }
  Tp<class T> void write(T x) {
    if (O > LIMIT) flush();
    if (x < 0) {
      quq[O++] = 45;
      x = -x;
    }
    do {
      ST[++sz] = x % 10 ^ 48;
      x /= 10;
    } while (x);
    while (sz) quq[O++] = ST[sz--];
  }
  FILEOUT& operator<<(int x) { return write(x), *this; }
} out;

int n, m;
const int maxn = 4e4 + 2;
bitset<maxn> qwq[42][42], qaq;
vector<int> g[maxn];
int a[maxn], b[maxn], sz[maxn], son[maxn], mxd[maxn], dep[maxn], fa[maxn];
int id[maxn], cnt = 0;

void dfs(int u) {
  sz[u] = 1, mxd[u] = dep[u];
  for (int v : g[u])
    if (!dep[v]) {
      dep[v] = dep[u] + 1, fa[v] = u;
      dfs(v), sz[u] += sz[v];
      cmax(mxd[u], mxd[v]);
      if (sz[v] > sz[son[u]]) son[u] = v;
    }
  if (mxd[u] - dep[u] >= 1000) id[u] = ++cnt, mxd[u] = dep[u];
}

int ff[maxn], st[maxn], top = 0;

void dfs2(int u) {
  for (int v : g[u])
    if (dep[v] > dep[u]) {
      if (id[v]) {
        int ip = id[st[top]], in = id[v];
        for (int x = v; x != st[top]; x = fa[x]) qwq[ip][in].set(a[x]);
        qaq = qwq[ip][in];
        for (int i = 1; i < top; i++) {
        	qwq[id[st[i]]][in] = qwq[id[st[i]]][ip];
					qwq[id[st[i]]][in] |= qaq;
				}
        ff[v] = st[top], st[++top] = v;
      }
      dfs2(v);
      if (id[v]) --top;
    }
}

int tp[maxn];
void dfs3(int u, int t) {
  tp[u] = t;
  if (son[u]) dfs3(son[u], t);
  for (int v : g[u])
    if (!tp[v]) dfs3(v, v);
}

int lca(int x, int y) {
  while (tp[x] != tp[y]) (dep[tp[x]] > dep[tp[y]]) ? x = fa[tp[x]] : y = fa[tp[y]];
  return dep[x] < dep[y] ? x : y;
}

void qwqwq(int x, int lca) {
  while (x != lca && !id[x]) qaq.set(a[x]), x = fa[x];
  if (x != lca) {
    int pre = x;
    while (dep[ff[pre]] >= dep[lca]) pre = ff[pre];
    if (pre != x) qaq |= qwq[id[pre]][id[x]];
    while (pre != lca) qaq.set(a[pre]), pre = fa[pre];
  }
}

int qry(int x, int y) {
  int Lca = lca(x, y);
  qaq.reset(), qaq.set(a[Lca]);
  qwqwq(x, Lca), qwqwq(y, Lca);
  return qaq.count();
}

signed main() {
  // code begin.
  in >> n >> m;
  rep(i, 1, n) in >> a[i], b[i] = a[i];
  sort(b + 1, b + n + 1);
  int len = unique(b + 1, b + n + 1) - b - 1;
  rep(i, 1, n) a[i] = lower_bound(b + 1, b + len + 1, a[i]) - b;
  rep(i, 2, n) {
    int u, v;
    in >> u >> v, g[u].pb(v), g[v].pb(u);
  }
  dfs(dep[1] = 1);
  if (!id[1]) id[1] = ++cnt;
  st[++top] = 1, dfs2(1), dfs3(1, 1);
  int ans = 0;
  while (m--) {
    int u, v;
    in >> u >> v, u ^= ans;
    out << (ans = qry(u, v)) << '\n';
  }
  return 0;
  // code end.
}