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| #include <cstdio>
#include <cmath>
#include <vector>
#include <algorithm>
using namespace std;
template <class Type>
void read(Type &x)
{
char c;
bool flag = false;
while ((c = getchar()) < '0' || c > '9')
c == '-' && (flag = true);
x = c - '0';
while ((c = getchar()) >= '0' && c <= '9')
x = (x << 3) + (x << 1) + c - '0';
flag && (x = ~x + 1);
}
template <class Type>
void write(Type x)
{
if (x < 0)
{
putchar('-');
x = ~x + 1;
}
if (x > 9)
write(x / 10);
putchar('0' + x % 10);
}
const int N = 4e4 + 10, M = N << 1, Q = 1e5 + 10, K = 18;
bool vis[N];
int n, m, len, w[N];
int res, cnt[N], ans[Q];
int stmp, s[M], fir[N], sec[N];
int idx, hd[N], nxt[M], edg[M];
namespace LCA
{
int lg[M];
int stmp, d[N], id[N], st[M][K];
void dfs(int x, int fa)
{
st[++stmp][0] = x;
d[x] = d[fa] + 1;
id[x] = stmp;
for (int i = hd[x]; ~i; i = nxt[i])
if (edg[i] != fa)
{
dfs(edg[i], x);
st[++stmp][0] = x;
}
}
int dmin(int x, int y)
{
return d[x] < d[y] ? x : y;
}
void init()
{
dfs(1, 0);
for (int i = 2; i <= stmp; i++)
lg[i] = lg[i >> 1] + 1;
for (int k = 1; (1 << k) <= stmp; k++)
for (int i = 1; i + (1 << k) - 1 <= stmp; i++)
st[i][k] = dmin(st[i][k - 1], st[i + (1 << k - 1)][k - 1]);
}
int lca(int x, int y)
{
x = id[x], y = id[y];
if (x > y)
swap(x, y);
int k = lg[y - x + 1];
return dmin(st[x][k], st[y - (1 << k) + 1][k]);
}
}
struct Query
{
int l, r, p, id;
friend bool operator<(const Query &x, const Query &y)
{
if (x.l / len != y.l / len)
return x.l < y.l;
return (x.l / len) & 1 ? (x.r < y.r) : (x.r > y.r);
}
} q[Q];
void add(int a, int b)
{
nxt[++idx] = hd[a];
hd[a] = idx;
edg[idx] = b;
}
void dfs(int x, int fa)
{
s[++stmp] = x;
fir[x] = stmp;
for (int i = hd[x]; ~i; i = nxt[i])
if (edg[i] != fa)
dfs(edg[i], x);
s[++stmp] = x;
sec[x] = stmp;
}
void add(int x)
{
vis[x] ^= 1;
if (!vis[x])
{
cnt[w[x]]--;
if (!cnt[w[x]])
res--;
}
else
{
if (!cnt[w[x]])
res++;
cnt[w[x]]++;
}
}
int main()
{
read(n), read(m);
vector<int> ws;
for (int i = 1; i <= n; i++)
{
read(w[i]);
ws.push_back(w[i]);
}
sort(ws.begin(), ws.end());
ws.erase(unique(ws.begin(), ws.end()), ws.end());
for (int i = 1; i <= n; i++)
w[i] = lower_bound(ws.begin(), ws.end(), w[i]) - ws.begin();
for (int i = 1; i <= n; i++)
hd[i] = -1;
for (int i = 1, u, v; i < n; i++)
{
read(u), read(v);
add(u, v);
add(v, u);
}
dfs(1, 0);
LCA::init();
for (int i = 0, a, b; i < m; i++)
{
read(a), read(b);
if (fir[a] > fir[b])
swap(a, b);
q[i].id = i;
int p = LCA::lca(a, b);
if (a == p)
q[i].l = fir[a], q[i].r = fir[b];
else
q[i].l = sec[a], q[i].r = fir[b], q[i].p = p;
}
len = max(1.0, stmp / sqrt(m));
sort(q, q + m);
for (int i = 0, l = 1, r = 0; i < m; i++)
{
while (r < q[i].r)
add(s[++r]);
while (l > q[i].l)
add(s[--l]);
while (r > q[i].r)
add(s[r--]);
while (l < q[i].l)
add(s[l++]);
if (q[i].p)
add(q[i].p);
ans[q[i].id] = res;
if (q[i].p)
add(q[i].p);
}
for (int i = 0; i < m; i++)
{
write(ans[i]);
puts("");
}
return 0;
}
|