Submission #999432

#	Time	Username	Problem	Language	Result	Execution time	Memory
999432		amine_aroua	Highway Tolls (IOI18_highway)	C++17	51 / 100	220 ms	262144 KiB

highway

#include<bits/stdc++.h>
using namespace std;
#define intt long long
#define pb push_back
#define forr(i , x , y) for(int i = x; i <= y;i++)
#define fore(i , n) for(int i = 0 ; i < n;i++)
#define forn(i ,x , y) for(int i = x ; i >= y;i--)
long long ask(const vector<int> &w);
void answer(int s, int t);
const int MAXN = 90001;
intt a , b;
vector<pair<int ,int>> adj[MAXN];
vector<int> zeros , ones;
vector<int> nodes;
vector<pair<int ,int>> nds;
intt val;
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
void dfs(int x , int p  , intt dep)
{
    if(dep == (val/b))
    {
        nodes.pb(x);
        return;
    }
    for(auto [u , i] : adj[x])
    {
        if(u == p)
            continue;
        dfs(u , x ,dep + 1 );
    }
}
void dfs1(int x , int p , int dep)
{
    nds.pb({dep , x});
    for(auto u : adj[x])
    {
        if(u.first == p)
            continue;
        dfs1(u.first , x , dep + 1);
    }
}
int findT(int S)
{
    dfs(S , -1  , 0);
    int l = 0 , r = (int)nodes.size();
    vector<int> asked = ones;
    while(l + 1 < r)
    {
        int mid = (l + r)/2;
        asked = ones;
        forr(j , 0 , mid - 1) {
            for(auto [u , i] : adj[nodes[j]])
                asked[i] = 0;
        }
        if(ask(asked) == val)
            l = mid;
        else
            r = mid;
    }
    return nodes[l];
}
void find_pair(int N, vector<int> U, vector<int> V, int A, int B)
{

    a = A , b = B;
    int m = (int)U.size();
    zeros.assign(m , 0);
    ones.assign(m , 1);
    fore(i , N)adj[i].clear();
    val = ask(ones);
    fore(i , m)
    {
        adj[U[i]].pb({V[i] , i});
        adj[V[i]].pb({U[i] , i});
    }
    dfs1(0 , -1 , 0);
    sort(nds.rbegin() , nds.rend());
    int l = 0 , r = (int)nds.size();
    vector<int> asked = ones;
    while(l + 1 < r)
    {
        int mid = (l + r)/2;
        asked = ones;
        forr(j , 0 , mid - 1) {
            for(auto i : adj[nds[j].second])asked[i.second] = 0;
        }
        if(ask(asked) == val)
            l = mid;
        else
            r = mid;
    }
    int S = nds[l].second;
    answer(S , findT(S));
}

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