# |
Submission time |
Handle |
Problem |
Language |
Result |
Execution time |
Memory |
846669 |
2023-09-08T08:46:41 Z |
vjudge1 |
Torrent (COI16_torrent) |
C++14 |
|
588 ms |
26788 KB |
#include<bits/stdc++.h>
using namespace std;
#define ll long long
const int ar = 3e5 + 5;
int n, a, b, par[ar];
vector<int> adj[ar];
int dp[ar];
int del, ans = 1e9;
void build_tree(int u, int p) {
for(int v : adj[u]) if(v != p){
par[v] = u;
build_tree(v, u);
}
}
void dfs(int u, int p) {
dp[u] = 0;
priority_queue<int> q;
for(int v : adj[u]) if(v != p && v != del) {
dfs(v, u);
q.push(dp[v]);
}
int cnt = 1;
while(q.size()) {
dp[u] = max(dp[u], cnt + q.top());
q.pop();
++cnt;
}
}
bool check1(int u, int v) {
del = v; dfs(a, 0);
del = u; dfs(b, 0);
ans = min(ans, max(dp[a], dp[b]));
return dp[u] >= dp[v];
}
bool check2(int u, int v) {
del = v; dfs(a, 0);
del = u; dfs(b, 0);
ans = min(ans, max(dp[a], dp[b]));
return dp[v] >= dp[u];
}
int main() {
ios::sync_with_stdio(0);
cin.tie(0); cout.tie(0);
cin >> n >> a >> b;
for(int i = 1; i < n; ++i) {
int x, y; cin >> x >> y;
adj[x].push_back(y);
adj[y].push_back(x);
}
build_tree(a, 0);
if(a == b) {
dfs(a, 0);
return cout << dp[a], 0;
}
vector<int> road;
int tmp = b; while(tmp != a) {
road.push_back(tmp);
tmp = par[tmp];
}
// if(n <= 1000) {
// for(int x : road) check1(par[x], x);
// return cout << ans, 0;
// }
int l = 0, r = road.size() - 1;
while(l <= r) {
int mid = l + r >> 1;
if(check1(par[road[mid]], road[mid])) l = mid + 1;
else r = mid - 1;
}
l = 0, r = road.size() - 1;
while(l <= r) {
int mid = l + r >> 1;
if(check2(par[road[mid]], road[mid])) r = mid - 1;
else l = mid + 1;
}
cout << ans;
}
Compilation message
torrent.cpp: In function 'int main()':
torrent.cpp:72:21: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
72 | int mid = l + r >> 1;
| ~~^~~
torrent.cpp:78:21: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
78 | int mid = l + r >> 1;
| ~~^~~
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Incorrect |
2 ms |
8540 KB |
Output isn't correct |
2 |
Halted |
0 ms |
0 KB |
- |
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Correct |
588 ms |
22032 KB |
Output is correct |
2 |
Correct |
576 ms |
23800 KB |
Output is correct |
3 |
Correct |
506 ms |
26696 KB |
Output is correct |
4 |
Correct |
548 ms |
24800 KB |
Output is correct |
5 |
Correct |
555 ms |
21648 KB |
Output is correct |
6 |
Correct |
477 ms |
21864 KB |
Output is correct |
7 |
Correct |
506 ms |
26788 KB |
Output is correct |