# |
Submission time |
Handle |
Problem |
Language |
Result |
Execution time |
Memory |
916583 |
2024-01-26T06:37:29 Z |
406 |
Torrent (COI16_torrent) |
C++17 |
|
441 ms |
29480 KB |
#include <bits/stdc++.h>
using namespace std;
const int N = 3e5 + 50;
bitset<N> mark;
vector<int> adj[N];
int par[N], n, a, b, dp[N];
void dfs_path(int v) {
mark[v] = true;
for (auto u: adj[v])
if (!mark[u]) {
par[u] = v;
dfs_path(u);
}
}
void dfs(int v) {
mark[v] = true;
vector<int> vc;
for (auto u: adj[v]) {
if (!mark[u]) {
dfs(u);
vc.push_back(dp[u]);
}
}
sort(vc.rbegin(), vc.rend());
dp[v] = 0;
for (int i = 0; i < vc.size(); i++)
dp[v] = max(dp[v], vc[i] + i + 1);
}
int check(int a, int O) {
mark = 0;
mark[O] = true;
dfs(a);
return dp[a];
}
signed main() {
ios::sync_with_stdio(0), cin.tie(0);
cin >> n >> a >> b;
assert(a != b);
a--, b--;
for (int i = 1; i < n; i++) {
int u, v;
cin >> u >> v;
u--, v--;
adj[u].push_back(v);
adj[v].push_back(u);
}
dfs_path(a);
vector<int> path{b};
while (path.back() != a)
path.push_back(par[path.back()]);
int l = 0, r = path.size() - 1;
while (r - l > 3) {
int mid = (r + l) / 2;
if (check(b, path[mid + 1]) > check(a, path[mid]))
r = mid;
else
l = mid;
}
int ans = n;
for (; l < r; l++)
ans = min(ans, max(check(b, path[l + 1]), check(a, path[l])));
cout << ans << '\n';
return 0;
}
Compilation message
torrent.cpp: In function 'void dfs(int)':
torrent.cpp:29:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
29 | for (int i = 0; i < vc.size(); i++)
| ~~^~~~~~~~~~~
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Correct |
3 ms |
9564 KB |
Output is correct |
2 |
Correct |
3 ms |
9564 KB |
Output is correct |
3 |
Correct |
4 ms |
9564 KB |
Output is correct |
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Correct |
395 ms |
26008 KB |
Output is correct |
2 |
Correct |
441 ms |
27560 KB |
Output is correct |
3 |
Correct |
361 ms |
29420 KB |
Output is correct |
4 |
Correct |
373 ms |
28728 KB |
Output is correct |
5 |
Correct |
351 ms |
25604 KB |
Output is correct |
6 |
Correct |
287 ms |
26080 KB |
Output is correct |
7 |
Correct |
310 ms |
29480 KB |
Output is correct |