Submission #594345

#	Time	Username	Problem	Language	Result	Execution time	Memory
594345		SlavicG	Highway Tolls (IOI18_highway)	C++17	11 / 100	621 ms	262144 KiB

highway

#include "highway.h"
#include "bits/stdc++.h"
using namespace std;
using ll = long long;
#define sz(a) (int)a.size()

const int N = 90010;
vector<int> adj[N];
int depth[N], p[N];
void dfs(int u, int par) {
    p[u] = par;
    for(int v: adj[u]) {
        if(v == par) continue;
        depth[v] = depth[u] + 1;
        dfs(v, u);
    }
}
int find(int start, int n, vector<int> u, vector<int> v) {
    map<pair<int, int>, int> idx;
    for(int i = 0; i < N; ++i) {
        adj[i].clear();
        depth[i] = 0;
        p[i] = -1;
    }

    int m = u.size();
    for(int i = 0; i < m; ++i) {
        adj[u[i]].push_back(v[i]);
        adj[v[i]].push_back(u[i]);
        idx[{u[i], v[i]}] = idx[{v[i], u[i]}] = i;
    }
    dfs(start, -1);
    int l = 1, r = n, dd = -1;
    vector<int> c(m, 1);
    ll init = ask(c);
    while(l <= r) {
        int mid = l + r >> 1;
        for(int j = 0; j < n; ++j) {
            if(depth[j] >= mid) {
                c[idx[{j, p[j]}]] = 0;
            }
        }
        if(ask(c) < init) {
            dd = mid;
            l = mid + 1;
        } else r = mid - 1;
        c.assign(m, 1);
    }
    vector<int> nodes;
    for(int i = 0; i < n; ++i) {
        if(depth[i] == dd) nodes.push_back(i);
    }
    assert(sz(nodes) > 0);

    l = 0, r = sz(nodes) - 1;
    int pp = -1;
    while(l <= r) {
        int mid = l + r >> 1;
        for(int i = 0; i <= mid; ++i) {
            assert(p[nodes[i]] != -1);
            c[idx[{nodes[i], p[nodes[i]]}]] = 0;
        }
        if(ask(c) < init) {
            pp = mid;
            r = mid - 1;
        } else l = mid + 1;
        c.assign(m, 1);
    }
    assert(pp != -1);
    return nodes[pp];
}
void find_pair(int n, vector<int> u, vector<int> v, int a, int b) {
    int s = find(0, n, u, v);
    int t = find(s, n, u, v);
    answer(t, s);
}

Compilation message (stderr)

highway.cpp: In function 'int find(int, int, std::vector<int>, std::vector<int>)':
highway.cpp:37:21: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
   37 |         int mid = l + r >> 1;
      |                   ~~^~~
highway.cpp:58:21: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
   58 |         int mid = l + r >> 1;
      |                   ~~^~~

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