Submission #766040

#	Time	Username	Problem	Language	Result	Execution time	Memory
766040		t6twotwo	Highway Tolls (IOI18_highway)	C++17	100 / 100	208 ms	11140 KiB

highway

#include "highway.h"
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
void find_pair(int N, vector<int> U, vector<int> V, int A, int B) {
    int M = U.size(), lo, hi;
    ll s = ask(vector<int>(M));
    vector<vector<pair<int, int>>> adj(N);
    for (int i = 0; i < M; i++) {
        adj[U[i]].emplace_back(V[i], i);
        adj[V[i]].emplace_back(U[i], i);
    }
    vector<int> W(M);
    lo = 0, hi = M - 1;
    while (lo < hi) {
        int mi = (lo + hi) / 2;
        auto w = W;
        for (int i = 0; i <= mi; i++) {
            w[i] = 1;
        }
        if (ask(w) == s) {
            W = w;
            lo = mi + 1;
        } else {
            hi = mi;
        }
    }
    auto bfs = [&](int s) {
        vector<int> dis(N, -1);
        dis[s] = 0;
        queue<int> q;
        q.push(s);
        while (!q.empty()) {
            int x = q.front();
            q.pop();
            for (auto [y, z] : adj[x]) {
                if (dis[y] == -1) {
                    dis[y] = dis[x] + 1;
                    q.push(y);
                }
            }
        }
        return dis;
    };
    int P = U[lo], Q = V[lo];
    auto d0 = bfs(P);
    auto d1 = bfs(Q);
    vector<int> cand;
    for (int i = 0; i < N; i++) {
        if (d0[i] < d1[i]) {
            cand.push_back(i);
        }
    }
    sort(cand.begin(), cand.end(), [&](int i, int j) {
        return d0[i] < d0[j];
    });
    lo = 0, hi = cand.size() - 1;
    while (lo < hi) {
        int mi = (lo + hi) / 2;
        vector<int> w(M);
        for (int i = mi + 1; i < cand.size(); i++) {
            for (auto [y, z] : adj[cand[i]]) {
                w[z] = 1;
            }
        }
        if (ask(w) == s) {
            hi = mi;
        } else {
            lo = mi + 1;
        }
    }
    int S = cand[lo];
    cand.clear();
    for (int i = 0; i < N; i++) {
        if (d1[i] < d0[i]) {
            cand.push_back(i);
        }
    }
    sort(cand.begin(), cand.end(), [&](int i, int j) {
        return d1[i] < d1[j];
    });
    lo = 0, hi = cand.size() - 1;
    while (lo < hi) {
        int mi = (lo + hi) / 2;
        vector<int> w(M);
        for (int i = mi + 1; i < cand.size(); i++) {
            for (auto [y, z] : adj[cand[i]]) {
                w[z] = 1;
            }
        }
        if (ask(w) == s) {
            hi = mi;
        } else {
            lo = mi + 1;
        }
    }
    answer(S, cand[lo]);
}

Compilation message (stderr)

highway.cpp: In function 'void find_pair(int, std::vector<int>, std::vector<int>, int, int)':
highway.cpp:61:32: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   61 |         for (int i = mi + 1; i < cand.size(); i++) {
      |                              ~~^~~~~~~~~~~~~
highway.cpp:86:32: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   86 |         for (int i = mi + 1; i < cand.size(); i++) {
      |                              ~~^~~~~~~~~~~~~

• Subtask 1: 5 / 5
• Subtask 2: 7 / 7
• Subtask 3: 6 / 6
• Subtask 4: 33 / 33
• Subtask 5: 18 / 18
• Subtask 6: 31 / 31