Submission #1219077

#	Time	Username	Problem	Language	Result	Execution time	Memory
1219077		JooDdae	Highway Tolls (IOI18_highway)	C++20	90 / 100	415 ms	25396 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();
    vector<vector<array<int, 2>>> v(N);
    for(int i=0;i<M;i++) {
        v[U[i]].push_back({V[i], i});
        v[V[i]].push_back({U[i], i});
    }

    auto query = [&](vector<vector<int>> L) {
        vector<int> w(M, 0);
        for(auto v : L) for(auto x : v) w[x] = 1;
        return ask(w);
    };

    auto bfs = [&](int s) -> pair<vector<int>, vector<vector<int>>> {
        vector<int> d(N, -1);
        vector<vector<int>> p(N);

        queue<int> q;
        q.push(s), d[s] = 0;
        while(!q.empty()) {
            int u = q.front(); q.pop();
            for(auto [x, id] : v[u]) {
                if(d[x] == -1) q.push(x), d[x] = d[u]+1;
                if(d[x] == d[u]+1) p[x].push_back(id);
            }
        }

        return {d, p};
    };

    ll D = query({});

    auto find_deepest = [&](int s) {
        auto [d, p] = bfs(s);

        vector<array<int, 2>> L(N);
        for(int i=0;i<N;i++) L[i] = {d[i], i};
        sort(L.rbegin(), L.rend());

        vector<vector<int>> P(N);
        for(int i=0;i<N;i++) P[i] = p[L[i][1]];
        
        int l = 1, r = N-1;
        while(l <= r) {
            int mid = (l+r) >> 1;
            if(query(vector<vector<int>>(P.begin(), P.begin()+mid)) == D) l = mid+1;
            else r = mid-1;
        }

        return L[r][1];
    };

    int P = find_deepest(rand() % N);
    int S = find_deepest(P);
    int T = find_deepest(S);

    answer(S, T);
}

• Subtask 1: 5 / 5
• Subtask 2: 7 / 7
• Subtask 3: 6 / 6
• Subtask 4: 33 / 33
• Subtask 5: 18 / 18
• Subtask 6: 21 / 31