Submission #920750

#	Time	Username	Problem	Language	Result	Execution time	Memory
920750		Whisper	Mag (COCI16_mag)	C++17	120 / 120	451 ms	213612 KiB

mag

#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';
    }
}

• Subtask 1: 12 / 12
• Subtask 2: 12 / 12
• Subtask 3: 12 / 12
• Subtask 4: 12 / 12
• Subtask 5: 12 / 12
• Subtask 6: 12 / 12
• Subtask 7: 12 / 12
• Subtask 8: 12 / 12
• Subtask 9: 12 / 12
• Subtask 10: 12 / 12