Submission #1021439

#	Time	Username	Problem	Language	Result	Execution time	Memory
1021439		Zicrus	Highway Tolls (IOI18_highway)	C++17	0 / 100	100 ms	9616 KiB

highway

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

typedef long long ll;

vector<vector<pair<int, int>>> adj;
vector<pair<int, int>> sorted;
vector<bool> vst;
vector<int> nDist;

void dfs(int a, int dist) {
    if (vst[a]) return;
    vst[a] = true;

    nDist[a] = dist - 1;

    for (auto &e : adj[a]) {
        if (vst[e.first]) continue;
        sorted.push_back({dist, e.second});
        dfs(e.first, dist + 1);
    }
}

void find_pair(int N, vector<int> U, vector<int> V, int A, int B) {
    int M = U.size();
    adj = vector<vector<pair<int, int>>>(N);
    sorted = vector<pair<int, int>>();
    for (int i = 0; i < M; i++) {
        adj[U[i]].push_back({V[i], i});
        adj[V[i]].push_back({U[i], i});
    }

    vst = vector<bool>(N);
    nDist = vector<int>(N);
    dfs(0, 1);
    sort(sorted.begin(), sorted.end());

    vector<int> tst(M);
    ll ctrl = ask(tst);

    int begin = 0;
    int end = M - 1;
    while (begin < end) {
        vector<int> w(M);
        int mid = (begin + end + 1) / 2;
        for (int i = mid; i <= end; i++) {
            w[sorted[i].second] = 1;
        }
        ll res = ask(w);
        if (res > ctrl) {
            begin = mid;
        }
        else {
            end = mid - 1;
        }
    }

    pair<int, int> sEdge = sorted[begin];
    int S = 0;
    for (int i = 0; i < N; i++) {
        bool hasS = false, further = nDist[i] == sEdge.first;
        for (auto &e : adj[i]) {
            if (e.second == sEdge.second) hasS = true;
        }
        if (hasS && further) {
            S = i;
            break;
        }
    }

    //cout << S << '\n';

    vst = vector<bool>(N);
    nDist = vector<int>(N);
    sorted = vector<pair<int, int>>();
    dfs(S, 1);
    sort(sorted.begin(), sorted.end());

    begin = -1;
    for (int i = 0; i < M; i++) {
        if (sorted[i].first == ctrl && begin == -1) begin = i;
        if (sorted[i].first == ctrl) end = i;
    }
    while (begin < end) {
        vector<int> w(M);
        int mid = (begin + end + 1) / 2;
        for (int i = mid; i <= end; i++) {
            w[sorted[i].second] = 1;
        }
        ll res = ask(w);
        if (res > ctrl) {
            begin = mid;
        }
        else {
            end = mid - 1;
        }
    }

    pair<int, int> tEdge = sorted[begin];
    int T = 0;
    for (int i = 0; i < N; i++) {
        bool hasT = false, further = nDist[i] == tEdge.first;
        for (auto &e : adj[i]) {
            if (e.second == tEdge.second) hasT = true;
        }
        if (hasT && further) {
            T = i;
            break;
        }
    }

    answer(S, T);
}

• Subtask 1: 0 / 5
• Subtask 2: 0 / 7
• Subtask 3: 0 / 6
• Subtask 4: 0 / 33
• Subtask 5: 0 / 18
• Subtask 6: 0 / 31