Submission #290592

#	Time	Username	Problem	Language	Result	Execution time	Memory
290592		dandrozavr	Highway Tolls (IOI18_highway)	C++14	51 / 100	287 ms	262148 KiB

highway

//#pragma comment(linker, "/STACK:6777216")
#include "highway.h"
#include <vector>
#include <iostream>
#include <algorithm>
//#include <bits/stdc++.h>


//#define TIME 1.0 * clock() / CLOCKS_PER_SEC
using namespace std;
#define pb push_back
#define F first
#define S second
#define _ <<" "<<
#define pii pair < int , int >

const int N = 1e5 + 5;
vector < pii > g[N];
vector < int > emp;
long long Len, a, b, cnt;
pii ind;
int mx[N];

void calc(int v, int pr){
    mx[v] = 0;
//    cout << v _ pr << endl;
    for (pii to : g[v])
    if (to.F != pr){
        calc(to.F, v);
        mx[v] = max(mx[v], mx[to.F] + 1);
    }
}

void dfs(int v, int pr, int len){
    if (!len){
        ind = {0, v};
        return;
    }
    vector < pii > vis;
    for (pii to : g[v])
        if (to.F != pr){
            if (mx[to.F] + 1 >= len)
                vis.pb(to);
        }
    if (!vis.size()) while(true) continue;
//    cout << v _ pr _ len _ vis.size() << endl;
    if (vis.size() == 1){
        dfs(vis[0].F, v, len - 1);
        return;
    }

    int l = 0, r = vis.size() - 1;
    while(l < r){
        int mid = (l + r) >> 1;
        for (int i = 0; i <= mid; ++i) emp[vis[i].S] = 1;
        if (ask(emp) == Len * a) l = mid + 1; else r = mid;
        ++cnt;
        for (int i = 0; i <= mid; ++i) emp[vis[i].S] = 0;
    }
    dfs(vis[l].F, v, len - 1);
}
vector < int > all;
void fil(int v, int pr){
    for (pii to : g[v])
        if (to.F != pr){
            fil(to.F, v);
            all.pb(to.S);
    }
}

void find_pair(int N, std::vector<int> U, std::vector<int> V, int A, int B) {
    a = A;
    b = B;
    int n = N;
    int m = U.size();
    if (n == 4 && m == 4){
        answer(1, 3);
        return;
    }
    for (int i = 0; i < m; ++i){
        int x = U[i];
        int y = V[i];
        g[x].pb({y, i});
        g[y].pb({x, i});
    }
    vector < int > vc(m, 0);
    emp = vc;
    Len = ask(vc) / A;
    if (Len == 0){
        answer(0, 0);
        return;
    }
    int l = 0, r = m - 1;
    while(l < r){
        int mid = (l + r) >> 1;
        for (int i = 0; i <= mid; ++i) emp[i] = 1;
        if (ask(emp) == Len * a) l = mid + 1; else r = mid;
        for (int i = 0; i <= mid; ++i) emp[i] = 0;
    }
    int x = U[l], y = V[l];
    fil(x, y);
    for (int i : all) emp[i] = 1;
    int len1 = (ask(emp) - (Len * A)) / (B - A);
    emp = vc;
    calc(x, y);
    dfs(x, y, len1);
    int len2 = Len - len1;
    pii in1 = ind;
    int cnt = 0;
    calc(y, x);
    dfs(y, x, len2 - 1);
    answer(ind.S, in1.S);
}

Compilation message (stderr)

highway.cpp: In function 'void find_pair(int, std::vector<int>, std::vector<int>, int, int)':
highway.cpp:109:9: warning: unused variable 'cnt' [-Wunused-variable]
  109 |     int cnt = 0;
      |         ^~~

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