Submission #421642

#	Time	Username	Problem	Language	Result	Execution time	Memory
421642		xt0r3	Highway Tolls (IOI18_highway)	C++14	51 / 100	258 ms	262148 KiB

highway

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

constexpr int N = 1e5 + 5;
vector<int> w, lst;
vector<pair<int, int> > edges[N];

int n, m, a, b, d[N], s, t;
long long alap;

void dfs(int id, int de = 0, int par = -1){
    d[id] = de;
    for(pair<int, int> p : edges[id]){
        if(p.first != par){
            dfs(p.first, de + 1, id);
            lst.push_back(p.second);
        }
    }
}

int src(int l, int r){
    if(l == r) return (l == lst.size() ? -1 : lst[l]);
    int m = (l + r) / 2;

    for(int i = max(0, l); i <= m; i++) w[lst[i]] = 1;
    long long cur = ask(w);
    for(int i = max(0, l); i <= m; i++) w[lst[i]] = 0;

    return (cur > alap ? src(l, m) : src(m + 1, r));

}

void find_pair(int _N, std::vector<int> u, std::vector<int> v, int A, int B) {
    n = _N;
    m = u.size();
    a = A;
    b = B;
    w.assign(m, 0);
    alap = ask(w);
    for(int i = 0; i < m; i++){
        edges[u[i]].emplace_back(v[i], i);
        edges[v[i]].emplace_back(u[i], i);
    }
    dfs(0);
    sort(lst.begin(), lst.end(), [&u, &v](int x, int y){return max(d[u[x]], d[v[x]]) > max(d[u[y]], d[v[y]]);});
    int id = src(0, lst.size() - 1);
    pair<int, int> p1 = make_pair(u[id], v[id]), p2;

    lst.clear();
    dfs(p1.first, 0, p1.second);
    if(lst.empty()){
        s = p1.first;
    }
    else{
        sort(lst.begin(), lst.end(), [&u, &v](int x, int y){return max(d[u[x]], d[v[x]]) > max(d[u[y]], d[v[y]]);});
        id = src(0, lst.size());
        if(id == -1) s = p1.first;
        else s = (d[u[id]] > d[v[id]] ? u[id] : v[id]);
    }

    swap(p1.first, p1.second);//ugyanez forditva
    lst.clear();
    dfs(p1.first, 0, p1.second);
    if(lst.empty()){
        t = p1.first;
    }
    else{
        sort(lst.begin(), lst.end(), [&u, &v](int x, int y){return max(d[u[x]], d[v[x]]) > max(d[u[y]], d[v[y]]);});
        id = src(0, lst.size());
        if(id == -1) t = p1.first;
        else t = (d[u[id]] > d[v[id]] ? u[id] : v[id]);
    }
    lst.clear();

  answer(s, t);
}

Compilation message (stderr)

highway.cpp: In function 'int src(int, int)':
highway.cpp:23:26: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   23 |     if(l == r) return (l == lst.size() ? -1 : lst[l]);
      |                        ~~^~~~~~~~~~~~~

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