#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;
using T = tuple<ll, ll, ll>;
#define int long long
#define Base 41
#define sz(a) (int)a.size()
#define FOR(i, a, b) for ( int i = a ; i <= b ; i++ )
#define FORD(i, a, b) for (int i = b; i >= a; i --)
#define REP(i, n) for (int i = 0; i < n; ++i)
#define REPD(i, n) for (int i = n - 1; i >= 0; --i)
#define all(x) x.begin() , x.end()
#define pii pair<int , int>
#define fi first
#define se second
#define Lg(x) 31 - __builtin_clz(x)
#define MASK(i) (1LL << (i))
#define BIT(x, i) (((x) >> (i)) & 1)
constexpr ll LINF = (1ll << 60);
constexpr int INF = (1ll << 30);
constexpr int MAX = 1e6 + 5;
constexpr int Mod = 1e9 + 7;
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
void setupIO(){
#define name "Whisper"
//Phu Trong from Nguyen Tat Thanh High School for gifted student
srand(time(NULL));
cin.tie(nullptr)->sync_with_stdio(false); cout.tie(nullptr);
//freopen(name".inp", "r", stdin);
//freopen(name".out", "w", stdout);
cout << fixed << setprecision(10);
}
template <class X, class Y>
bool minimize(X &x, const Y &y){
X eps = 1e-9;
if (x > y + eps) {x = y; return 1;}
return 0;
}
template <class X, class Y>
bool maximize(X &x, const Y &y){
X eps = 1e-9;
if (x + eps < y) {x = y; return 1;}
return 0;
}
int N;
int a[MAX];
vector<int> adj[MAX];
struct Data{
int x, y;
Data(){}
Data(int _x, int _y): x(_x), y(_y){}
friend bool operator < (const Data& a, const Data& b){
return a.x * b.y < b.x * a.y;
}
friend ostream& operator << (ostream& cout, const Data& a){
int g = __gcd(a.x, a.y);
cout << a.x / g << "/" << a.y / g;
return cout;
}
};
Data ans(1e9, 1);
int up[MAX];
int down[2][MAX];
void dfs_down(int u, int p){
for (auto&v : adj[u]) if(v ^ p){
//tìm đường đi gồm toàn số 1 dài nhất và dài nhì kết thúc tại v
dfs_down(v, u);
if (a[v] == 1){
if (down[0][u] < down[0][v] + 1){
down[1][u] = down[0][u];
down[0][u] = down[0][v] + 1;
}
else if(down[1][u] < down[0][v] + 1){
down[1][u] = down[0][v] + 1;
}
}
}
}
void dfs_up(int u, int p){
for (auto&v : adj[u]) if(v ^ p){
if(a[u] == 1){
//tìm đường đi dài nhất bắt đầu từ u lên root
up[v] = up[u] + 1;
if (a[v] == 1){
if (down[0][v] + 1 == down[0][u]){
maximize(up[v], down[1][u] + 1);
}
}
else maximize(up[v], down[0][u] + 1);
}
dfs_up(v, u);
}
vector<int> store;
store.push_back(up[u]);
store.push_back(down[1][u]);
store.push_back(down[0][u]);
sort(all(store), greater<int>());
ans = min(ans, Data(a[u], store[0] + store[1] + 1));
}
void Whisper(){
cin >> N;
for (int i = 1; i < N; ++i){
int u, v; cin >> u >> v;
adj[u].push_back(v);
adj[v].push_back(u);
}
for (int i = 1; i <= N; ++i) cin >> a[i];
dfs_down(1, 0);
dfs_up(1, 0);
cout << ans;
}
signed main(){
setupIO();
int Test = 1;
// cin >> Test;
for ( int i = 1 ; i <= Test ; i++ ){
Whisper();
if (i < Test) cout << '\n';
}
}
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
6 ms |
24924 KB |
Output is correct |
2 |
Correct |
8 ms |
26968 KB |
Output is correct |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
7 ms |
26972 KB |
Output is correct |
2 |
Correct |
7 ms |
27220 KB |
Output is correct |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
334 ms |
121444 KB |
Output is correct |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
6 ms |
26972 KB |
Output is correct |
2 |
Correct |
451 ms |
210044 KB |
Output is correct |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
422 ms |
192064 KB |
Output is correct |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
417 ms |
86344 KB |
Output is correct |
2 |
Correct |
250 ms |
86608 KB |
Output is correct |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
316 ms |
88760 KB |
Output is correct |
2 |
Correct |
59 ms |
37972 KB |
Output is correct |
3 |
Correct |
435 ms |
213612 KB |
Output is correct |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
57 ms |
36460 KB |
Output is correct |
2 |
Correct |
348 ms |
87244 KB |
Output is correct |
3 |
Correct |
292 ms |
70612 KB |
Output is correct |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
423 ms |
84416 KB |
Output is correct |
2 |
Correct |
353 ms |
102880 KB |
Output is correct |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
380 ms |
87252 KB |
Output is correct |
2 |
Correct |
301 ms |
70596 KB |
Output is correct |