Submission #594418

#	Time	Username	Problem	Language	Result	Execution time	Memory
594418		SlavicG	Highway Tolls (IOI18_highway)	C++17	90 / 100	934 ms	59504 KiB

highway

#include "highway.h"
#include "bits/stdc++.h"
using namespace std;
using ll = long long;
#define sz(a) (int)a.size()
#define all(a) a.begin(),a.end()
#define rall(a) a.rbegin(),a.rend()

void dfs(int u, int par, vector<vector<int>>& adj, vector<int>& p, vector<int>& depth) {
    p[u] = par;
    for(int v: adj[u]) {
        if(v == par) continue;
        depth[v] = depth[u] + 1;
        dfs(v, u, adj, p, depth);
    }
}
void bfsTree(int start, vector<vector<int>>& adj, vector<vector<int>>& g) {
    queue<int> q; q.push(start);
    vector<bool> vis(sz(g), 0);
    vis[start] = 1;
    while(!q.empty()) {
        int u = q.front();
        q.pop();
        for(int v: g[u]) {
            if(!vis[v]) {
                adj[u].push_back(v);
                adj[v].push_back(u);
                vis[v] = true;
                q.push(v);
            }
        }
    }
}
ll init;
map<vector<int>, ll> mp;
ll query(vector<int>& c) {
    if(!mp.count(c)) mp[c] = ask(c);
    return mp[c];
}
int find(int start, int n, vector<int>& u, vector<int>& v) {
    map<pair<int, int>, int> idx;
    vector<vector<int>> adj(n), g(n);
    vector<int> p(n, 0), depth(n, 0);

    int m = u.size();
    for(int i = 0; i < m; ++i) {
        g[u[i]].push_back(v[i]);
        g[v[i]].push_back(u[i]);
        idx[{u[i], v[i]}] = idx[{v[i], u[i]}] = i;
    }
    bfsTree(start, adj, g);
    dfs(start, -1, adj, p, depth);
    int l = 1, r = n, dd = -1;
    vector<int> c(m, 1);
    for(int i = 0; i < n; ++i) {
        if(p[i] != -1) c[idx[{i, p[i]}]] = 0;
    }

    vector<pair<int, int>> bruh(n);
    for(int i = 0; i < n; ++i) {
        bruh[i] = {depth[i], i};
    }
    sort(rall(bruh));
    vector<int> nodes;
    for(int i = 0; i < n; ++i) {
        nodes.push_back(bruh[i].second);
    }
    assert(sz(nodes) > 0);

    l = 0, r = sz(nodes) - 1;
    int pp = -1;
    vector<int> rem = c;
    vector<int> ids(n, -1);
    for(int i = 0; i < n; ++i) {
        ids[i] = idx[{nodes[i], p[nodes[i]]}];
    }
    while(l <= r) {
        int mid = (l + r) >> 1;
        for(int i = 0; i <= mid; ++i) {
            if(p[i] == -1) continue;
            c[ids[i]] = 1;
        }
        if(query(c) > init) {
            pp = mid;
            r = mid - 1;
        } else l = mid + 1;
        c = rem;
    }
    assert(pp != -1);
    return nodes[pp];
}
void find_pair(int n, vector<int> u, vector<int> v, int a, int b) {
    vector<int> noo(sz(u), 0);
    init = query(noo);

    int pos = -1, l = 0, r = sz(u) - 1;
    while(l <= r) {
        int mid = (l + r) >> 1;
        for(int i = 0; i <= mid; ++i) noo[i] = 1;
        if(query(noo) > init) {
            pos = mid;
            r = mid - 1;
        } else l = mid + 1;

        for(int i = 0; i <= mid; ++i) noo[i] = 0;
    }
    assert(pos != -1);
    int node = u[pos];
    int s = find(node, 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:53:23: warning: unused variable 'dd' [-Wunused-variable]
   53 |     int l = 1, r = n, dd = -1;
      |                       ^~

• Subtask 1: 5 / 5
• Subtask 2: 7 / 7
• Subtask 3: 6 / 6
• Subtask 4: 33 / 33
• Subtask 5: 18 / 18
• Subtask 6: 21 / 31