/**
* code generated by JHelper
* More info: https://github.com/AlexeyDmitriev/JHelper
* @author win11905
*/
#include <bits/stdc++.h>
#define all(x) (x).begin(), (x).end()
#define long long long
#define pii pair<int, int>
#define x first
#define y second
using namespace std;
const long MOD = 1e9+7, LINF = 1e18 + 1e16;
const int INF = 1e9+1;
const double EPS = 1e-10;
const int dx[4] = {-1, 0, 1, 0}, dy[4] = {0, 1, 0, -1};
const int N = 3e5+5;
class torrent {
private:
int n, a, b;
int vl[N], par[N];
vector<int> g[N];
void dfs(int u, int p) {
par[u] = p;
for(int e : g[u]) if(e != p)
dfs(vl[e] ^ u, e);
}
int dp[N], bad;
void mic(int u, int p) {
vector<int> ret;
for(int e : g[u]) if(e != p && e != bad) {
mic(vl[e] ^ u, e);
ret.emplace_back(dp[vl[e] ^ u]);
}
sort(all(ret), greater<int>());
for(int i = 0; i < ret.size(); ++i) dp[u] = max(dp[u], ret[i]+i+1);
}
int calc(int val) {
memset(dp, 0, sizeof dp);
bad = val;
mic(a, 0), mic(b, 0);
return max(dp[a], dp[b]);
}
public:
void solve(istream& cin, ostream& cout) {
cin >> n >> a >> b;
for(int i = 1, u, v; i < n; ++i) {
cin >> u >> v;
vl[i] = u ^ v;
g[u].emplace_back(i), g[v].emplace_back(i);
}
dfs(b, 0);
vector<int> vec;
int x = a;
while(x != b) {
vec.emplace_back(par[x]);
x = vl[par[x]] ^ x;
}
int l = 0, r = vec.size()-1;
while(l < r) {
int m = l + r >> 1;
if(calc(vec[m]) <= calc(vec[m+1])) r = m;
else l = m+1;
}
cout << calc(vec[r]);
}
};
class Solver {
public:
void solve(std::istream& in, std::ostream& out) {
torrent *obj = new torrent();
obj->solve(in, out);
}
};
int main() {
ios::sync_with_stdio(false);
cin.tie(0);
Solver solver;
std::istream& in(std::cin);
std::ostream& out(std::cout);
solver.solve(in, out);
return 0;
}
Compilation message
torrent.cpp: In member function 'void torrent::mic(int, int)':
torrent.cpp:39:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
for(int i = 0; i < ret.size(); ++i) dp[u] = max(dp[u], ret[i]+i+1);
~~^~~~~~~~~~~~
torrent.cpp: In member function 'void torrent::solve(std::istream&, std::ostream&)':
torrent.cpp:64:14: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
int m = l + r >> 1;
~~^~~
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Incorrect |
14 ms |
11000 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Incorrect |
1187 ms |
23868 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
