#include<iostream>
#include<queue>
#include<stack>
#include<algorithm>
#include<string.h>
#define task
#define size() size() * 1ll
#define all(x) (x).begin(), (x).end()
#define allr(x, sz) (x) + 1, (x) + 1 + sz
#define pb push_back
#define pii pair<int,int>
#define fi first
#define se second
#define MASK(x) (1LL<<(x))
#define BIT(x,i) (((x)>>(i))&1)
#define numbit(x) __builtin_popcountll(x)
using namespace std;
const int N = 1e6 + 1;
const int M = 1e3 + 1;
const long long mod = 1e9 + 7;
const long long oo = 1e18 + 7;
typedef vector<int> vi;
typedef vector<pii> vii;
typedef long long ll;
template<class t>
bool mini(t &x,t y) {
if (x > y) {
x = y;
return 1;
}
return 0;
}
template<class t>
bool maxi(t &x,t y) {
if (x < y) {
x = y;
return 1;
}
return 0;
}
void file() {
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
//freopen(task.in, r, stdin);
//freopen(task.out, w, stdout);
return ;
}
int n, a, b;
int cha[N], cl[N], dp[N];
vi adj[N];
void dfs(int u, int chu) {
cha[u] = chu;
for (auto v: adj[u]) if (v != chu) {
dfs(v, u);
}
}
void calc(int u, int chu, int clr) {
dp[u] = 0;
vi val;
for (auto v: adj[u]) if (v != chu && cl[v] != clr) {
calc(v, u, clr);
val.pb(dp[v]);
}
sort(all(val), greater<int>());
for (int i = 0; i < val.size(); i++) {
maxi(dp[u], val[i] + i + 1);
}
}
void solve(int test = -1) {
cin >> n >> a >> b;
for (int i = 1; i < n; i++) {
int x, y;
cin >> x >> y;
adj[x].pb(y);
adj[y].pb(x);
}
dfs(a, 0);
vi node;
for (int i = b; i; i = cha[i]) {
node.pb(i);
}
reverse(all(node));
int l = 0, r = node.size() - 1;
int res = l;
while (l <= r) {
int mid = l + r >> 1;
for (int i = 0; i <= mid; i++) {
cl[node[i]] = 1;
}
for (int i = mid + 1; i < node.size(); i++) {
cl[node[i]] = 2;
}
calc(a, -1, 2);
calc(b, -1, 1);
if (dp[a] <= dp[b]) {
l = mid + 1;
res = mid;
} else r = mid - 1;
}
for (int i = 0; i <= res; i++) {
cl[node[i]] = 1;
}
for (int i = res + 1; i < node.size(); i++) {
cl[node[i]] = 2;
}
calc(a, -1, 2);
calc(b, -1, 1);
int ans = max(dp[a], dp[b]);
if (res + 1 < node.size()) {
for (int i = 0; i <= res + 1; i++) {
cl[node[i]] = 1;
}
for (int i = res + 2; i < node.size(); i++) {
cl[node[i]] = 2;
}
calc(a, -1, 2);
calc(b, -1, 1);
mini(ans, max(dp[a], dp[b]));
}
cout << ans;
}
int32_t main() {
file();
int T = 1;
// cin >> T;
for (int i = 1; i <= T; i++) {
solve(i);
}
return 0;
}
Compilation message
torrent.cpp: In function 'void calc(int, int, int)':
torrent.cpp:71:23: warning: comparison of integer expressions of different signedness: 'int' and 'long long unsigned int' [-Wsign-compare]
71 | for (int i = 0; i < val.size(); i++) {
| ^
torrent.cpp: In function 'void solve(int)':
torrent.cpp:92:21: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
92 | int mid = l + r >> 1;
| ~~^~~
torrent.cpp:96:33: warning: comparison of integer expressions of different signedness: 'int' and 'long long unsigned int' [-Wsign-compare]
96 | for (int i = mid + 1; i < node.size(); i++) {
| ^
torrent.cpp:109:29: warning: comparison of integer expressions of different signedness: 'int' and 'long long unsigned int' [-Wsign-compare]
109 | for (int i = res + 1; i < node.size(); i++) {
| ^
torrent.cpp:115:17: warning: comparison of integer expressions of different signedness: 'int' and 'long long unsigned int' [-Wsign-compare]
115 | if (res + 1 < node.size()) {
| ^
torrent.cpp:119:33: warning: comparison of integer expressions of different signedness: 'int' and 'long long unsigned int' [-Wsign-compare]
119 | for (int i = res + 2; i < node.size(); i++) {
| ^
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
12 ms |
23764 KB |
Output is correct |
| 2 |
Correct |
13 ms |
23812 KB |
Output is correct |
| 3 |
Correct |
14 ms |
23764 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
438 ms |
42444 KB |
Output is correct |
| 2 |
Correct |
408 ms |
43744 KB |
Output is correct |
| 3 |
Correct |
427 ms |
45492 KB |
Output is correct |
| 4 |
Correct |
435 ms |
44724 KB |
Output is correct |
| 5 |
Correct |
403 ms |
41988 KB |
Output is correct |
| 6 |
Correct |
401 ms |
42704 KB |
Output is correct |
| 7 |
Correct |
388 ms |
46076 KB |
Output is correct |
