Submission #995479

#	Time	Username	Problem	Language	Result	Execution time	Memory
995479		shiomusubi496	Highway Tolls (IOI18_highway)	C++17	100 / 100	146 ms	12220 KiB

highway

#include "highway.h"
#include <bits/stdc++.h>

#define rep(i, n) for (int i = 0; i < (int)(n); ++i)
#define rep2(i, a, b) for (int i = (int)(a); i < (int)(b); ++i)
#define rrep(i, n) for (int i = (int)(n) - 1; i >= 0; --i)
#define rrep2(i, a, b) for (int i = (int)(b) - 1; i >= (int)(a); --i)
#define all(v) begin(v), end(v)
#define rall(v) rbegin(v), rend(v)

using namespace std;

using ll = long long;

template<class T, class U> bool chmin(T& a, const U& b) { return a > b ? a = b, true : false; }
template<class T, class U> bool chmax(T& a, const U& b) { return a < b ? a = b, true : false; }

mt19937 mt(random_device{}());

struct edge {
    int to, idx;
    edge() = default;
    edge(int t, int i) : to(t), idx(i) {}
};

void find_pair(int N, std::vector<int> U, std::vector<int> V, int A, int B) {
    int M = U.size();
    vector<vector<edge>> G(N);
    rep (i, M) {
        G[U[i]].emplace_back(V[i], i);
        G[V[i]].emplace_back(U[i], i);
    }
    ll dist = ask(vector<int>(M, 0));

    int s;
    {
        int ok = 0, ng = M;
        while (ng - ok > 1) {
            int mid = (ok + ng) / 2;
            vector<int> f(M);
            rep (i, M) f[i] = i < mid;
            if (ask(f) != dist) ng = mid;
            else ok = mid;
        }
        // ok 本目までの辺で最短経路のカットになる
        // 以下 ok 未満の辺は全て B として、 ok の各端点につながる頂点を探す
        s = ok;
    }
    int sv0 = U[s], sv1 = V[s];
    // sv0 から行く方が sv1 からより近い頂点集合の中に v0 がいる
    vector<int> dist1(N, -1), dist2(N, -1);
    queue<int> que;
    dist1[sv0] = 0;
    que.push(sv0);
    while (!que.empty()) {
        int v = que.front(); que.pop();
        for (auto e : G[v]) {
            if (dist1[e.to] == -1 && e.idx > s) {
                dist1[e.to] = dist1[v] + 1;
                que.push(e.to);
            }
        }
    }
    dist2[sv1] = 0;
    que.push(sv1);
    while (!que.empty()) {
        int v = que.front(); que.pop();
        for (auto e : G[v]) {
            if (dist2[e.to] == -1 && e.idx > s) {
                dist2[e.to] = dist2[v] + 1;
                que.push(e.to);
            }
        }
    }
    vector<int> near0(N);
    rep (i, N) {
        if (dist1[i] != -1 && (dist2[i] == -1 || dist1[i] < dist2[i])) near0[i] = 1;
        if (dist2[i] != -1 && (dist1[i] == -1 || dist2[i] < dist1[i])) near0[i] = -1;
    }
    // 遠い辺から無効にしていったとき、はじめて距離が変わったときの辺の端点が答え？
    int ans0, ans1;
    {
        vector<pair<int, int>> es;
        rep2 (i, s + 1, M) {
            if (near0[U[i]] != 1 || near0[V[i]] != 1) continue;
            int d = max(dist1[U[i]], dist1[V[i]]);
            es.emplace_back(d, i);
        }
        sort(rall(es));
        int ok = es.size() + 1, ng = 0;
        while (ok - ng > 1) {
            int mid = (ok + ng) / 2;
            vector<int> f(M);
            rep (i, s) f[i] = 1;
            rep (i, mid) f[es[i].second] = 1;
            if (ask(f) != dist) ok = mid;
            else ng = mid;
        }
        if (ok == es.size() + 1) ans0 = sv0;
        else {
            --ok;
            if (dist1[U[es[ok].second]] > dist1[V[es[ok].second]]) ans0 = U[es[ok].second];
            else ans0 = V[es[ok].second];
        }
    }
    {
        vector<pair<int, int>> es;
        rep2 (i, s + 1, M) {
            if (near0[U[i]] != -1 || near0[V[i]] != -1) continue;
            int d = max(dist2[U[i]], dist2[V[i]]);
            es.emplace_back(d, i);
        }
        sort(rall(es));
        int ok = es.size() + 1, ng = 0;
        while (ok - ng > 1) {
            int mid = (ok + ng) / 2;
            vector<int> f(M);
            rep (i, s) f[i] = 1;
            rep (i, mid) f[es[i].second] = 1;
            if (ask(f) != dist) ok = mid;
            else ng = mid;
        }
        if (ok == es.size() + 1) ans1 = sv1;
        else {
            --ok;
            if (dist2[U[es[ok].second]] > dist2[V[es[ok].second]]) ans1 = U[es[ok].second];
            else ans1 = V[es[ok].second];
        }
    }
    answer(ans0, ans1);
}

Compilation message (stderr)

highway.cpp: In function 'void find_pair(int, std::vector<int>, std::vector<int>, int, int)':
highway.cpp:99:16: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   99 |         if (ok == es.size() + 1) ans0 = sv0;
      |             ~~~^~~~~~~~~~~~~~~~
highway.cpp:123:16: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  123 |         if (ok == es.size() + 1) ans1 = sv1;
      |             ~~~^~~~~~~~~~~~~~~~

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