제출 #1199154

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
1199154		repsak	Highway Tolls (IOI18_highway)	C++20	0 / 100	4 ms	716 KiB

highway

#include "highway.h"
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;

void dfs(int node, int parent, vector<vector<pair<int, int>>> &adj, vector<int>& depths, vector<pair<int, int>> &sameDepths, int dist){

    for(auto [v, i] : adj[node]){
        if(v == parent) continue;
        depths[v] = depths[node] + 1;
        if(depths[v] == dist){
            sameDepths.push_back({v, i});
            continue;
        }
        dfs(v, node, adj, depths, sameDepths, dist);
    }
}

int bSearch(vector<pair<int, int>>& sameDepths, int M, int dist, ll cost){
    int l = 0; int r = sameDepths.size();
    vector<int> w(M, 0);

    while(l < r){
        int mid = (l + r) / 2;

        for(int i = l; i <= mid; i++){
            w[sameDepths[i].second] = 1;
        }

        ll newDist = ask(w);

        if(newDist == cost){
            l = mid + 1;
        }else{
            for(int i = mid; i < r; i++){
                w[sameDepths[i].second] = 0;
            }
            r = mid;
        }
    }

    return sameDepths[l].first;
}

pair<int, int> search(int N, vector<int> U, vector<int> V, int A, int B){
    int M = U.size();
    vector<int> initial(M, 0);
    ll initialCost = ask(initial);
    int distance = initialCost / A;

    vector<vector<pair<int, int>>> adj;
    for(int i = 0; i < M; i++){
        int u = U[i]; int v = V[i];
        adj[u].push_back({v, i});
        adj[v].push_back({u, i});
    }

    vector<int> depths(M, 0);
    vector<pair<int, int>> sameDepth;
    dfs(0, 0, adj, depths, sameDepth, distance);

    int secondLocation = bSearch(sameDepth, M, distance, initialCost);
    return {0, secondLocation};
}

void find_pair(int N, std::vector<int> U, std::vector<int> V, int A, int B) {

  pair<int, int> ans = search(N, U, V, A, B);
  answer(ans.first, ans.second);
}

// #include "grader.cpp"
// #include "grader.cpp"

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