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| ##include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;
typedef pair<int, int> pdd;
##define INF 0x3f3f3f3f
##define lowbit(x) x & (-x)
##define mem(a, b) memset(a , b , sizeof(a))
##define FOR(i, x, n) for(int i = x;i <= n; i++)
const int N = 2e5 + 10;
int n;
struct Edge {
int u, v, next;
}e[N << 1];
int idx, head[N << 1];
int fa[N][55], depth[N], lg[N];
struct Node {
int l, r;
int val;
}hjt[N * 40];
int a[N], root[N], cnt;
vector<int> vec;
inline void add(int u, int v) {
e[++idx].v = v;
e[idx].next = head[u];
head[u] = idx;
}
inline int getid(int x) { return lower_bound(vec.begin(), vec.end(), x) - vec.begin() + 1; }
void insert(int pre, int &now, int l, int r, int p) {
hjt[now = ++cnt] = hjt[pre];
hjt[now].val++;
if(l == r) return ;
int m = (l + r) / 2;
if(p <= m) insert(hjt[pre].l, hjt[now].l, l, m, p);
else insert(hjt[pre].r, hjt[now].r, m + 1, r, p);
}
int query(int ql, int qr, int lca, int falca, int l, int r, int k) {
if(l == r) return l;
int m = (l + r) / 2;
int tmp = hjt[hjt[ql].l].val + hjt[hjt[qr].l].val - hjt[hjt[lca].l].val - hjt[hjt[falca].l].val;
if(k <= tmp) return query(hjt[ql].l, hjt[qr].l, hjt[lca].l, hjt[falca].l, l, m, k);
else return query(hjt[ql].r, hjt[qr].r, hjt[lca].r, hjt[falca].r, m + 1, r, k - tmp);
}
int LCA(int u1, int u2) {
if(depth[u1] < depth[u2]) swap(u1, u2);
while(depth[u1] > depth[u2])
u1 = fa[u1][lg[depth[u1] - depth[u2]] - 1];
if(u1 == u2) return u1;
for(int i = lg[depth[u1]] - 1;i >= 0; i--) {
if(fa[u1][i] != fa[u2][i]) {
u1 = fa[u1][i];
u2 = fa[u2][i];
}
}
return fa[u1][0];
}
void LCA_DFS(int u, int pre) {
fa[u][0] = pre;
depth[u] = depth[pre] + 1;
insert(root[pre], root[u], 1, n, getid(a[u]));
for(int i = 1;i <= lg[depth[u]]; i++) {
fa[u][i] = fa[fa[u][i - 1]][i - 1];
}
for(int i = head[u]; i; i = e[i].next) {
if(e[i].v != pre)
LCA_DFS(e[i].v, u);
}
}
void solve()
{
int m;
cin >> n >> m;
for(int i = 1;i <= n; i++) {
cin >> a[i]; vec.push_back(a[i]);
}
sort(vec.begin(), vec.end());
vec.erase(unique(vec.begin(), vec.end()), vec.end());
for(int i = 1;i < n; i++) {
int u, v;
cin >> u >> v;
add(u, v);
add(v, u);
}
for(int i = 1; i <= n; ++i)
lg[i] = lg[i - 1] + (1 << lg[i - 1] == i);
LCA_DFS(1, 0);
while(m--) {
int l, r, k;
cin >> l >> r >> k;
int lca = LCA(l, r);
cout << vec[query(root[l], root[r], root[lca], root[fa[lca][0]], 1, n, k) - 1] << endl;
}
}
signed main() {
ios_base::sync_with_stdio(false);
##ifdef FZT_ACM_LOCAL
freopen("in.txt", "r", stdin);
freopen("out.txt", "w", stdout);
signed test_index_for_debug = 1;
char acm_local_for_debug = 0;
do {
if (acm_local_for_debug == '$') exit(0);
if (test_index_for_debug > 20)
throw runtime_error("Check the stdin!!!");
auto start_clock_for_debug = clock();
solve();
auto end_clock_for_debug = clock();
cout << "Test " << test_index_for_debug << " successful" << endl;
cerr << "Test " << test_index_for_debug++ << " Run Time: "
<< double(end_clock_for_debug - start_clock_for_debug) / CLOCKS_PER_SEC << "s" << endl;
cout << "--------------------------------------------------" << endl;
} while (cin >> acm_local_for_debug && cin.putback(acm_local_for_debug));
##else
solve();
##endif
return 0;
}
|
