#define _CRT_SECURE_NO_WARNINGS
#include <bits/stdc++.h>
//#include <ext/pb_ds/tree_policy.hpp>
//#include <ext/pb_ds/assoc_container.hpp>
using namespace std;
//using namespace __gnu_pbds;
#define FOR(i,start,end) for(int i=start;i<(int)(end);i++)
#define FORE(i,start,end) for(int i=start;i<=(int)end;i++)
#define RFOR(i,start,end) for(int i = start; i>end; i--)
#define RFORE(i,start,end) for(int i = start; i>=end; i--)
#define all(a) a.begin(), a.end()
#define mt make_tuple
#define mp make_pair
#define v vector
#define sf scanf
#define pf printf
#define dvar(x) cout << #x << " := " << x << "\n"
#define darr(x,n) FOR(i,0,n) cout << #x << "[" << i << "]" << " := " << x[i] << "\n"
typedef long long ll;
typedef long double ld;
typedef pair<int, int > pii;
typedef pair<ll, ll> pll;
//template <class T> using ordered_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
template<class T> void minn(T &a, T b) { a = min(a, b); }
template<class T> void maxx(T &a, T b) { a = max(a, b); }
void io() {
#ifdef LOCAL_PROJECT
freopen("input.in", "r", stdin); freopen("output.out", "w", stdout);
#else
/* online submission */
#endif
ios_base::sync_with_stdio(false); cin.tie(NULL);
}
const ll MOD = 1000000007LL;
const ll PRIME = 105943LL;
const ll INF = 1e18;
/****************************************************************/
const int MAXN = 300099;
v<int> adj[MAXN];
int N, root1, root2;
bool findpath(int x, int p, int y, v<int> &path) {
path.push_back(x);
if (x == y) return 1;
for (int c : adj[x]) if (c != p)
if (findpath(c, x, y, path)) return 1;
path.pop_back();
return 0;
}
pii delEdge;
int dfsdp(int x, int p) {
int ans = 0;
v<int> dpc;
for (int c : adj[x]) if (c != p && mp(c, x) != delEdge && mp(x, c) != delEdge)
dpc.push_back(dfsdp(c, x));
sort(all(dpc)), reverse(all(dpc));
FOR(i, 0, dpc.size()) maxx(ans, dpc[i] + i + 1);
return ans;
}
v<int> path;
void change(int i) {
if (i < path.size() - 1) delEdge = { path[i], path[i + 1] };
else delEdge = { -1,-1 };
}
int main() {
io();
cin >> N >> root1 >> root2;
FOR(i, 0, N - 1) {
int x, y;
cin >> x >> y;
adj[x].push_back(y);
adj[y].push_back(x);
}
findpath(root1, -1, root2, path);
assert(path[0] == root1 && path.back() == root2);
//FOR(i, 0, path.size()) {
// if (i < path.size() - 1) delEdge = { path[i], path[i + 1] };
// else delEdge = { -1,-1 };
// // cout << i << ": " << dfsdp(root1, -1) << " " << dfsdp(root2, -1) << "\n";
// cout << i << ": " << (dfsdp(root1, -1) < dfsdp(root2, -1)) << "\n";
//}
change(0);
bool sign = dfsdp(root1, -1) < dfsdp(root2, -1);
int lo = 0, hi = path.size() - 1;
while (lo < hi) {
int mid = (lo + hi) / 2;
change(mid);
if ((dfsdp(root1, -1) < dfsdp(root2, -1)) == sign)
lo = mid + 1;
else
hi = mid;
}
int ans = INT_MAX;
FORE(i, lo - 5, lo + 5) if (0 <= lo && lo < path.size()) {
change(lo);
minn(ans, max(dfsdp(root1, -1), dfsdp(root2, -1)));
}
cout << ans << "\n";
return 0;
}
Compilation message
torrent.cpp: In function 'void change(int)':
torrent.cpp:70:8: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
if (i < path.size() - 1) delEdge = { path[i], path[i + 1] };
~~^~~~~~~~~~~~~~~~~
torrent.cpp: In function 'int main()':
torrent.cpp:107:44: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
FORE(i, lo - 5, lo + 5) if (0 <= lo && lo < path.size()) {
~~~^~~~~~~~~~~~~
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
8 ms |
7416 KB |
Output is correct |
| 2 |
Correct |
8 ms |
7556 KB |
Output is correct |
| 3 |
Correct |
10 ms |
7556 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
966 ms |
20696 KB |
Output is correct |
| 2 |
Correct |
853 ms |
22820 KB |
Output is correct |
| 3 |
Correct |
690 ms |
23024 KB |
Output is correct |
| 4 |
Correct |
825 ms |
24756 KB |
Output is correct |
| 5 |
Correct |
701 ms |
24756 KB |
Output is correct |
| 6 |
Correct |
716 ms |
24756 KB |
Output is correct |
| 7 |
Incorrect |
752 ms |
24864 KB |
Output isn't correct |
