Submission #1087824

#	Time	Username	Problem	Language	Result	Execution time	Memory
1087824		TrinhKhanhDung	Mag (COCI16_mag)	C++14	120 / 120	254 ms	116020 KiB

mag

#include <bits/stdc++.h>
#define ll long long
#define fi first
#define se second
#define sz(x) (int)x.size()
#define ALL(v) v.begin(),v.end()
#define MASK(k) (1LL << (k))
#define BIT(x, i) (((x) >> (i)) & 1)
#define oo (ll)1e18
#define INF (ll)1e9
#define MOD (ll)(1e9 + 7)

using namespace std;

template<class T1, class T2>
    bool maximize(T1 &a, T2 b){if(a < b){a = b; return true;} return false;}

template<class T1, class T2>
    bool minimize(T1 &a, T2 b){if(a > b){a = b; return true;} return false;}

template<class T1, class T2>
    void add(T1 &a, T2 b){a += b; if(a >= MOD) a -= MOD;}

template<class T1, class T2>
    void sub(T1 &a, T2 b){a -= b; if(a < 0) a += MOD;}

template<class T>
    void cps(T &v){sort(ALL(v)); v.resize(unique(ALL(v)) - v.begin());}

const int MAX = 1e6 + 10;

int N;
vector<int> adj[MAX];
int a[MAX], f[MAX], g[MAX];
vector<pair<int, int>> edges;
int ans;
int P, Q;

void dfs1(int u, int p = -1){
    int first = 0, second = 0;
    for(int v: adj[u]){
        if(v == p) continue;
        dfs1(v, u);
        if(f[v] > first){
            second = first;
            first = f[v];
        }
        else maximize(second, f[v]);
    }
    f[u] = first + 1;
    maximize(ans, first + second + 1);
}

void dfs2(int u, int p = -1){
    int first = g[u], second = 0;
    for(int v: adj[u]){
        if(v == p) continue;
        if(f[v] + 1 > first){
            second = first;
            first = f[v] + 1;
        }
        else{
            maximize(second, f[v] + 1);
        }
    }
    for(int v: adj[u]){
        if(v == p) continue;
        if(f[v] + 1 == first) g[v] = second + 1;
        else g[v] = first + 1;
        dfs2(v, u);
    }
}

void solve(){
    cin >> N;
    for(int i = 1; i < N; i++){
        int u, v; cin >> u >> v;
        edges.push_back(make_pair(u, v));
    }
    int mi = INF;
    for(int i = 1; i <= N; i++){
        cin >> a[i];
        minimize(mi, a[i]);
    }
    if(mi > 1){
        cout << mi << "/1\n";
        return;
    }
    for(auto o: edges){
        if(a[o.fi] != 1 || a[o.se] != 1) continue;
        adj[o.fi].push_back(o.se);
        adj[o.se].push_back(o.fi);
    }
    for(int i = 1; i <= N; i++) if(a[i] == 1 && f[i] == 0){
        dfs1(i);
        g[i] = 1;
        dfs2(i);
    }
    P = 1; Q = ans;
    for(auto o: edges){
        if(min(a[o.fi], a[o.se]) == 1 && max(a[o.fi], a[o.se]) == 2){
            adj[o.fi].push_back(o.se);
            adj[o.se].push_back(o.fi);
        }
    }
    for(int i = 1; i <= N; i++) if(a[i] == 2){
        int first = 0, second = 0;
        for(int j: adj[i]){
            int c = max(f[j], g[j]);
            if(c > first){
                second = first;
                first = c;
            }
            else{
                maximize(second, c);
            }
        }
        if(1LL * P * (second * 2 + 1) > 1LL * Q * 2){
            P = 2;
            Q = second * 2 + 1;
        }
    }
    cout << P << "/" << Q << '\n';
}

int main(){
    ios_base::sync_with_stdio(0); cin.tie(0);
//    freopen("numtable.inp","r",stdin);
//    freopen("numtable.out","w",stdout);

    solve();

    return 0;
}

• 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