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182 lines (158 loc) · 4.36 KB
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// Ivan Carvalho
// Solution to https://dmoj.ca/problem/bts18p7
#include <bits/stdc++.h>
using namespace std;
const int MAXN = 1e5 + 10;
const int MAXL = 18;
vector<int> grafo[MAXN];
int ancestral[MAXN][MAXL], maior[MAXN][MAXL], menor[MAXN][MAXL];
int nivel[MAXN], populacao[MAXN], e1[MAXN], e2[MAXN], e3[MAXN];
int N, Q, R, maxH, LOGH;
void dfs(int v, int p) {
for (int i : grafo[v]) {
int u = (e1[i] != v) ? (e1[i]) : (e2[i]);
if (u == p) continue;
ancestral[u][0] = v;
nivel[u] = nivel[v] + 1;
maior[u][0] = max(populacao[v], populacao[u]);
menor[u][0] = e3[i];
dfs(u, v);
}
}
void build() {
for (int j = 1; j < MAXL; j++) {
for (int i = 1; i <= N; i++) {
int z = ancestral[i][j - 1];
if (z == -1) continue;
ancestral[i][j] = ancestral[z][j - 1];
maior[i][j] = max(maior[i][j - 1], maior[z][j - 1]);
menor[i][j] = min(menor[i][j - 1], menor[z][j - 1]);
}
}
}
int LCA(int v, int u) {
if (nivel[v] < nivel[u]) swap(u, v);
for (int i = LOGH; i >= 0; i--) {
int z = ancestral[v][i];
if (z == -1) continue;
if (nivel[z] >= nivel[u]) v = z;
}
if (u == v) return u;
for (int i = LOGH; i >= 0; i--) {
if (ancestral[v][i] != -1 && ancestral[v][i] != ancestral[u][i]) {
v = ancestral[v][i];
u = ancestral[u][i];
}
}
return ancestral[v][0];
}
int goUp(int v, int h) {
h = nivel[v] - h;
for (int i = LOGH; i >= 0; i--) {
int z = ancestral[v][i];
if (z == -1) continue;
if (nivel[z] >= h) v = z;
}
return v;
}
int maxPath(int v, int u) {
int ans = populacao[v];
for (int i = LOGH; i >= 0; i--) {
int z = ancestral[v][i];
if (z == -1) continue;
if (nivel[z] >= nivel[u]) {
ans = max(ans, maior[v][i]);
v = z;
}
}
return ans;
}
int minPath(int v, int u) {
int ans = Q + 1;
for (int i = LOGH; i >= 0; i--) {
int z = ancestral[v][i];
if (z == -1) continue;
if (nivel[z] >= nivel[u]) {
ans = min(ans, menor[v][i]);
v = z;
}
}
return ans;
}
int buscaSubiu(int v, int u, int k) {
// printf("Busca Subiu\n");
int ini = 0, fim = nivel[v] - nivel[u], meio, resp = -1;
while (ini <= fim) {
meio = (ini + fim) / 2;
// printf("I %d M %d F %d\n",ini,meio,fim);
int w = goUp(v, meio);
// printf("V %d W %d %d\n",v,w,maxPath(v,w));
if (maxPath(v, w) >= k) {
resp = meio;
fim = meio - 1;
} else {
ini = meio + 1;
}
}
return goUp(v, resp);
}
int buscaDesceu(int v, int u, int k) {
// printf("Busca Desceu\n");
int ini = 0, fim = nivel[v] - nivel[u], meio, resp = -1;
while (ini <= fim) {
meio = (ini + fim) / 2;
int w = goUp(v, meio);
if (maxPath(w, u) >= k) {
resp = meio;
ini = meio + 1;
} else {
fim = meio - 1;
}
}
return goUp(v, resp);
}
int main() {
scanf("%d %d %d", &N, &Q, &R);
for (int i = 1; i <= N; i++) scanf("%d", &populacao[i]);
for (int i = 1; i < N; i++) {
scanf("%d %d", &e1[i], &e2[i]);
e3[i] = Q + 1;
grafo[e1[i]].push_back(i);
grafo[e2[i]].push_back(i);
}
for (int i = 1; i <= R; i++) {
int x, y;
scanf("%d %d", &x, &y);
e3[y] = x;
}
for (int j = 0; j < MAXL; j++) {
for (int i = 0; i <= N; i++) {
menor[i][j] = Q + 1;
maior[i][j] = 0;
ancestral[i][j] = -1;
}
}
dfs(1, -1);
build();
for (int i = 1; i <= N; i++) maxH = max(maxH, nivel[i] + 1);
while ((1 << LOGH) <= maxH) LOGH++;
for (int q = 1; q <= Q; q++) {
int a, b, k;
scanf("%d %d %d", &a, &b, &k);
int c = LCA(a, b);
int meuMin = min(minPath(a, c), minPath(b, c));
int m1 = maxPath(a, c), m2 = maxPath(b, c);
int meuMax = max(m1, m2);
// printf("C %d com D %d e Min %d Max %d (%d,%d)\n",c,
nivel[a] + nivel[b] - 2*nivel[c], meuMin, meuMax,m1,m2);
if (q > meuMin || meuMax < k) {
printf("-1\n");
continue;
}
if (m1 >= k)
printf("%d\n", buscaSubiu(a, c, k));
else
printf("%d\n", buscaDesceu(b, c, k));
}
return 0;
}