Submission #765916

#	Time	Username	Problem	Language	Result	Execution time	Memory
765916		t6twotwo	Highway Tolls (IOI18_highway)	C++17	51 / 100	117 ms	10268 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);
            }
        }
        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++) {
                w[f0[cand[i]]] = 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++) {
                w[f1[cand[i]]] = 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