You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
70 lines
1.4 KiB
70 lines
1.4 KiB
#include <bits/stdc++.h>
|
|
using namespace std;
|
|
const int N = 40010, M = 80010;
|
|
int e[M], h[N], idx, ne[M];
|
|
void add(int a, int b) {
|
|
e[idx] = b, ne[idx] = h[a], h[a] = idx++;
|
|
}
|
|
// 暴力法可以过掉 6/10
|
|
int n;
|
|
int depth[N];
|
|
int fa[N];
|
|
|
|
void bfs(int root) {
|
|
queue<int> q;
|
|
q.push(root);
|
|
depth[root] = 1;
|
|
fa[root] = -1;
|
|
|
|
while (q.size()) {
|
|
int u = q.front();
|
|
q.pop();
|
|
for (int i = h[u]; ~i; i = ne[i]) {
|
|
int v = e[i];
|
|
if (!depth[v]) {
|
|
depth[v] = depth[u] + 1;
|
|
fa[v] = u;
|
|
q.push(v);
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
int lca(int a, int b) {
|
|
if (depth[a] < depth[b]) swap(a, b);
|
|
while (depth[a] < depth[b]) b = fa[b];
|
|
while (a != b) a = fa[a], b = fa[b];
|
|
return a;
|
|
}
|
|
|
|
int main() {
|
|
#ifndef ONLINE_JUDGE
|
|
freopen("1172.in", "r", stdin);
|
|
#endif
|
|
memset(h, -1, sizeof h);
|
|
|
|
scanf("%d", &n);
|
|
int a, b, m, root;
|
|
|
|
for (int i = 0; i < n; i++) {
|
|
scanf("%d %d", &a, &b);
|
|
if (b == -1)
|
|
root = a;
|
|
else
|
|
add(a, b), add(b, a);
|
|
}
|
|
bfs(root);
|
|
|
|
scanf("%d", &m);
|
|
while (m--) {
|
|
scanf("%d %d", &a, &b);
|
|
int p = lca(a, b);
|
|
if (p == a)
|
|
puts("1");
|
|
else if (p == b)
|
|
puts("2");
|
|
else
|
|
puts("0");
|
|
}
|
|
return 0;
|
|
} |