Submission #765928

#	Time	Username	Problem	Language	Result	Execution time	Memory
765928		t6twotwo	Highway Tolls (IOI18_highway)	C++17	51 / 100	132 ms	10276 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), f(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 && !W[z]) {
                    dis[y] = dis[x] + 1;
                    f[y] = z;
                    q.push(y);
                }
            }
        }
        return make_pair(dis, f);
    };
    int P = U[lo], Q = V[lo];
    auto [d0, f0] = bfs(P);
    auto [d1, f1] = bfs(Q);
    f0[P] = lo;
    f1[Q] = lo;
    vector<int> w(M, 1);
    vector<bool> vis(N);
    vis[P] = 1;
    for (int i = 0; i < N; i++) {
        if (d0[i] < d1[i] && d0[i] != -1) {
            int x = i;
            while (!vis[x]) {
                vis[x] = 1;
                w[f0[x]] = 0;
                x ^= U[f0[x]] ^ V[f0[x]];
            }
        }
    }
    int t = (s + (s / A) * (B - A) - ask(w)) / (B - A);
    vector<int> cand;
    for (int i = 0; i < N; i++) {
        if (d0[i] == t && d0[i] < d1[i] && d0[i] != -1) {
            cand.push_back(i);
        }
    }
    assert(ask(W) == s);
    lo = 0, hi = cand.size() - 1;
    while (lo < hi) {
        int mi = (lo + hi) / 2;
        vector<int> w = W;
        for (int i = 0; i <= mi; i++) {
            for (auto [y, z] : adj[cand[i]]) {
                if (d0[y] + 1 == d0[cand[i]]) {
                    w[z] = 1;
                }
            }
        }
        if (ask(w) == s + B - A) {
            hi = mi;
        } else {
            lo = mi + 1;
        }
    }
    int S = cand[lo];
    cand.clear();
    for (int i = 0; i < N; i++) {
        if (d1[i] == s / A - t - 1 && d1[i] < d0[i] && d1[i] != -1) {
            cand.push_back(i);
        }
    }
    lo = 0, hi = cand.size() - 1;
    while (lo < hi) {
        int mi = (lo + hi) / 2;
        vector<int> w = W;
        for (int i = 0; i <= mi; i++) {
            for (auto [y, z] : adj[cand[i]]) {
                if (d1[y] + 1 == d1[cand[i]]) {
                    w[z] = 1;
                }
            }
        }
        if (ask(w) == s + B - A) {
            hi = mi;
        } else {
            lo = mi + 1;
        }
    }
    answer(S, cand[lo]);
}

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