Submission #1191389

#TimeUsernameProblemLanguageResultExecution timeMemory
1191389MatteoArcariHighway Tolls (IOI18_highway)C++20
0 / 100
57 ms8120 KiB
#include <bits/stdc++.h> using namespace std; using ll = long long; ll ask(const vector<int> &w); void answer(int s, int t); void find_pair(int n, vector<int> u, vector<int> v, int a, int b) { int m = u.size(); vector<int> w(m); ll dst = ask(w) / a; vector<vector<int>> adj(n); for (int i = 0; i < m; i++) { adj[u[i]].push_back(i); adj[v[i]].push_back(i); } int s; { queue<int> q; vector<int> d(n, -1); for (int i = 0; i < n; i++) { if (adj[i].size() == 1) { d[i] = 0; q.push(i); } } while (!q.empty()) { int i = q.front(); q.pop(); for (int _j: adj[i]) { int j = u[_j] ^ v[_j] ^ i; if (d[j] == -1) { d[j] = d[i] + 1; q.push(j); } } } int mad = *max_element(d.begin(), d.end()); int mid = -1; for (int k = 1 << 30; k; k >>= 1) { if (mid + k >= mad) continue; vector<int> ww(m); for (int i = 0; i < m; i++) { if (d[u[i]] <= mid + k || d[v[i]] <= mid + k) ww[i] = 1; } if (ask(ww) == dst * a) mid += k; } vector<int> check; for (int i = 0; i < n; i++) { if (d[i] == mid + 1) check.push_back(i); } while (check.size() > 1) { for (auto &x: w) x = 0; for (int i = 0; i < check.size(); i++) { if (i & 1) { for (int _j: adj[check[i]]) { w[_j] = 1; } } } vector<int> cc; int flag = ask(w) > a * dst; for (int i = 0; i < check.size(); i++) { if (flag == i % 2) { cc.push_back(check[i]); } } check = cc; } s = check[0]; } vector<int> d(n, -1), check, p(n); d[s] = 0; queue<int> q; q.push(s); while (!q.empty()) { int i = q.front(); q.pop(); if (d[i] == dst) { check.push_back(i); continue; } for (int _j: adj[i]) { int j = u[_j] ^ v[_j] ^ i; if (d[j] == -1) { p[j] = _j; d[j] = d[i] + 1; q.push(j); } } } while (check.size() > 1) { for (auto &x: w) x = 0; for (int i = 0; i < check.size(); i++) { if (i & 1) { w[p[check[i]]] = 1; } } vector<int> cc; int flag = ask(w) > a * dst; for (auto i: check) { if (w[p[i]] == flag) { cc.push_back(i); } } check = cc; } assert(s == 0 || check[0] == 0); answer(s, check[0]); }
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