제출 #473740

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
473740		ntabc05101	Mag (COCI16_mag)	C++14	84 / 120	533 ms	186752 KiB

mag

#include<bits/stdc++.h>
using namespace std;

const int MAX = 1000000;

bool cmp(const pair<int, int> &a, const pair<int, int> &b) {
  return (long long)a.first * b.second < (long long)a.second * b.first;
}

int p[MAX];
int dpup[MAX], dpdown[MAX];
vector<int> L, R;
int lft[MAX], rgt[MAX];
vector<int> adj[MAX];
pair<int, int> res = {1e9, 1};

void dfsdown(int node, int par) {
  L.push_back(0);
  for (auto &it : adj[node]) {
    if (it != par) {
      dfsdown(it, node);
      lft[it] = (int)L.size() - 1;
      L.push_back(max(L.back(), p[it] == 1 ? dpdown[it] + 1 : 0));
    }
  }

  R.push_back(0);
  for (int i = (int)adj[node].size() - 1; i >= 0; i--) {
    int it = adj[node][i];
    if (it != par) {
      rgt[it] = (int)R.size() - 1;
      R.push_back(max(R.back(), p[it] == 1 ? dpdown[it] + 1 : 0));

      dpup[it] = (p[node] == 1 ? (1 + max(L[lft[it]], R[rgt[it]])): 0);
    }
  }

  dpdown[node] = L.back();
  L.clear(); R.clear();
}

void dfsup(int node, int par) {
  if (node) {
    dpup[node] = (p[par] == 1 ? max(dpup[node], 1 + dpup[par]) : 0);
  }

  pair<int, int> a = {p[node], 1};
  if (cmp(a, res)) {
    res = a;
  }
  int mx = dpup[node];

  for (auto &it : adj[node]) {
    if (it == par) {
      continue;
    }

    int val = (p[it] == 1 ? dpdown[it] + 1 : 0);
    pair<int, int> tmp = {p[node], 1 + mx + val};
    if (cmp(tmp, res)) {
      res = tmp;
    }
    mx = max(mx, val);
    dfsup(it, node);
  }
}

int main() {
  cin.tie(0)->sync_with_stdio(0);

  int n; cin >> n;
  for (int i = 0; i < n - 1; i++) {
    int a, b; cin >> a >> b;
    a--; b--;
    adj[a].push_back(b);
    adj[b].push_back(a);
  }

  for (int i = 0; i < n; i++) {
    cin >> p[i];
  }

  dfsdown(0, -1);
  dfsup(0, -1);

  int gc = __gcd(res.first, res.second);
  cout << res.first / gc << "/" << res.second / gc << endl;

  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: 0 / 12
• Subtask 8: 0 / 12
• Subtask 9: 12 / 12
• Subtask 10: 0 / 12