Submission #1219097

#	Time	Username	Problem	Language	Result	Execution time	Memory
1219097		JooDdae	Highway Tolls (IOI18_highway)	C++20	0 / 100	8 ms	1636 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<array<int, 2>> L) {
        vector<int> w(M, 0);
        for(auto [d, u] : L) for(auto [x, id] : v[u]) w[id] = 1;
        return ask(w);
    };

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

        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;
            }
        }

        return d;
    };

    ll D = query({});

    auto find_deepest = [&](int s, vector<int> e) {
        auto d = bfs(s);

        vector<array<int, 2>> L;
        for(auto x : e) L.push_back({d[x], x});
        sort(L.rbegin(), L.rend());

        int l = 1, r = (int)L.size()-1;
        while(l <= r) {
            int mid = (l+r) >> 1;
            if(query(vector<array<int, 2>>(L.begin(), L.begin()+mid)) == D) l = mid+1;
            else r = mid-1;
        }

        return L[r][1];
    };

    int l = 1, r = M-1;
    while(l <= r) {
        int mid = (l+r) >> 1;

        vector<int> w(M, 0);
        fill(w.begin(), w.begin()+mid+1, 1);

        if(ask(w) == D) l = mid+1;
        else r = mid-1;
    }
    int S = U[r], T = V[r];

    vector<int> d[2] = {bfs(S), bfs(T)}, e[2];
    for(int i=0;i<N;i++) e[d[0][i] > d[1][i]].push_back(i);

    int ans[2] = {-1, -1};
    for(int i=0;i<2;i++) ans[i] = find_deepest(i?T:S, e[i]);

    answer(ans[0], ans[1]);
}

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