#include "bits/stdc++.h"
using namespace std;
const int N = 2e5,
L = 18;
#ifndef LOCAL
#define cerr
if (0) cerr
#endif
int n, p[N];
int pp[L][N], d[N];
vector < int > g[N];
long long dp[N];
int f[N];
int uf(int i) {
return f[i] == i ? i : f[i] = uf(f[i]);
}
void dfs(int i) {
for (int l = 1; l < L; l++) pp[l][i] = pp[l - 1][pp[l - 1][i]];
for (int j: g[i])
if (pp[0][i] != j) {
pp[0][j] = i;
d[j] = d[i] + 1;
dfs(j);
}
}
int lca(int i, int j) {
if (d[i] < d[j]) swap(i, j);
int k = d[i] - d[j];
for (int l = 0; l < L; l++)
if (k >> l & 1) i = pp[l][i];
if (i == j) return i;
for (int l = L - 1; l >= 0; l--)
if (pp[l][i] != pp[l][j]) i = pp[l][i], j = pp[l][j];
return pp[0][i];
}
int dis(int i, int j) {
return d[i] + d[j] - 2 * d[lca(i, j)];
}
int main() {
cin >> n;
for (int i = 0; i < n; i++) cin >> p[i], p[i]--;
for (int h = 0; h < n - 1; h++) {
int i, j;
cin >> i >> j, i--, j--;
i = p[i], j = p[j];
cerr << "edge " << i << " " << j << endl;
g[i].push_back(j);
g[j].push_back(i);
}
pp[0][0] = 0;
dfs(0);
for (int i = 0; i < n; i++) f[i] = i;
for (int i = 0; i < n; i++) {
for (int j: g[i])
if (j < i) {
int c = uf(j);
cerr << c << " " << i << "|" << dis(c, i) << endl;
dp[i] = max(dp[i], dp[c] + dis(c, i));
f[c] = i;
}
cerr << "dp[" << i << "]=" << dp[i] << endl;
}
cout << * max_element(dp, dp + n) << '\n';
}
Compilation message
Main.cpp:10:1: error: expected unqualified-id before 'if'
10 | if (0) cerr
| ^~
Main.cpp: In function 'int main()':
Main.cpp:47:12: error: 'n' was not declared in this scope
47 | cin >> n;
| ^
Main.cpp:48:40: error: 'p' was not declared in this scope
48 | for (int i = 0; i < n; i++) cin >> p[i], p[i]--;
| ^
Main.cpp:52:13: error: 'p' was not declared in this scope
52 | i = p[i], j = p[j];
| ^
Main.cpp:53:14: error: expected primary-expression before '<<' token
53 | cerr << "edge " << i << " " << j << endl;
| ^~
Main.cpp:64:22: error: expected primary-expression before '<<' token
64 | cerr << c << " " << i << "|" << dis(c, i) << endl;
| ^~
Main.cpp:68:14: error: expected primary-expression before '<<' token
68 | cerr << "dp[" << i << "]=" << dp[i] << endl;
| ^~
