Submission #1055140

#	Time	Username	Problem	Language	Result	Execution time	Memory
1055140		Ahmed57	Highway Tolls (IOI18_highway)	C++17	5 / 100	196 ms	262144 KiB

highway

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

using namespace std;
pair<int,int> p[100001];
int dep[100001];
vector<pair<int,int>> adj[100001];
void dfs(int i,int pr,int id){
    dep[i] = dep[pr]+1;
    p[i] = {pr,id};
    for(auto j:adj[i]){
        if(j.first==pr)continue;
        dfs(j.first,i,j.second);
    }
}

void find_pair(int N, vector<int> U, vector<int> V, int A, int B){
    int m = U.size();
    vector<int> as(m,0);
    vector<int> as2(m,1);
    int len = ask(as);
    int len2 = ask(as2);
    for(int i = 0;i<U.size();i++){
        adj[U[i]].push_back({V[i],i});
        adj[V[i]].push_back({U[i],i});
    }
    dfs(0,0,-1);
    vector<pair<int,int>> v;
    for(int i = 0;i<N;i++){
        v.push_back({dep[i],i});
    }
    sort(v.begin(),v.end());
    reverse(v.begin(),v.end());
    int l = 0 , r = v.size()-2 , ans = 0;
    while(l<=r){
        int mid = (l+r)/2;
        vector<int> as(m,0);
        for(int i = 0;i<=mid;i++){
            as[p[v[i].second].second] = 1;
        }
        if(ask(as)!=len){
            ans = mid;
            r = mid-1;
        }else l = mid+1;
    }
    int a = v[ans].second;
    l = 2 , r = dep[a] ;int ans2 = -1; 
    while(l<=r){
        int mid = (l+r)/2;
        vector<int> as(m,0);
        for(int i = 0;i<N;i++){
            if(dep[i]>=mid){
                as[p[i].second] =1 ;
            }
        }
        int na = ask(as);
        if(na>len+(dep[a]-mid+1)*(B-A)){
            ans2 = mid;
            l = mid+1;
        }else r = mid-1;
    }
    if(ans2==-1){
        int x = len/A;
        int b = a;
        while(x--){
            b = p[b].first;
        }
        answer(a,b);
        return ;
    }
    vector<int> lol;
    l = -1;
    for(int i = 0;i<v.size();i++){
        if(v[i].first==ans2&&l==-1)l = i;
        if(v[i].first==ans2)r = i;
    }   
    int ans3 = 0;
    while(l<=r){
        int mid = (l+r)/2;
        vector<int> as(m,0);
        for(int i = 0;i<=mid;i++){
            as[p[v[i].second].second] = 1;
        }
        if(ask(as)==len+(dep[a]-ans2+1)*(B-A)+(B-A)){
            ans3 = mid;
            r = mid-1;
        }else l = mid+1;
    }
    int b = v[ans3].second;
    answer(a,b);
}

Compilation message (stderr)

highway.cpp: In function 'void find_pair(int, std::vector<int>, std::vector<int>, int, int)':
highway.cpp:23:20: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   23 |     for(int i = 0;i<U.size();i++){
      |                   ~^~~~~~~~~
highway.cpp:73:20: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   73 |     for(int i = 0;i<v.size();i++){
      |                   ~^~~~~~~~~
highway.cpp:22:9: warning: unused variable 'len2' [-Wunused-variable]
   22 |     int len2 = ask(as2);
      |         ^~~~

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