Submission #417952

#	Time	Username	Problem	Language	Result	Execution time	Memory
417952		temurbek_khujaev	Race (IOI11_race)	C++17	0 / 100	4 ms	5708 KiB

race

#include "race.h"
#include <bits/stdc++.h>

#define N 200200
using namespace std;

vector<pair<int, int> > g[N];
int d[N];
int p[N];

int get_centroid(int v, int parent, int n, int &centroid) {
    int size = 1;
    for (auto[x, y]:g[v]) {
        if (x != parent && d[x] == -1) {
            size += get_centroid(x, v, n, centroid);
        }
    }
    if (size * 2 >= n && centroid == -1) centroid = v;
    return size;
}

int K;
int ans = 1e9;

void get_compo_dists(int v, int dist, int len, int pass_limit, vector<pair<int, int> > &vec, int p = -1) {
    if (dist > K) return;
    vec.emplace_back(dist, len);
    for (auto[x, y]:g[v]) {
        if ((d[x] > pass_limit || d[x] == -1) && p != x) {
            get_compo_dists(x, dist + y, len + 1, pass_limit, vec, v);
        }
    }
}

void build(int v, int parent, int depth, int n) {
    int centroid = -1;
    get_centroid(v, -1, n, centroid);
    if (centroid == -1) centroid = v;
    d[centroid] = depth;
    p[centroid] = parent;
    map<int, int> dist;
    dist[0] = 0;

    for (auto[x, y]:g[centroid]) {
        if (d[x] == -1) {
            build(x, centroid, depth + 1, (n + 1) / 2);
            vector<pair<int, int>> vec;
            get_compo_dists(centroid, 0, 0, d[centroid], vec);
            for (auto[distance, cost]: vec) {
                if (dist.count(K - distance)) {
                    ans = min(ans, cost + dist[distance]);
                }
            }

            for (auto[distance, cost]: vec) {
                if (dist.count(distance) == 0) {
                    dist[distance] = cost;
                } else dist[distance] = min(dist[distance], cost);
            }
        }


    }
//    cerr << "Centroid = " << centroid << endl;
//    for (auto[x, y]:dist) {
//        cerr << x << ' ' << y << endl;
//    }
}

int best_path(int n, int K, int H[][2], int L[]) {
    ::K = K;
    for (int i = 0; i < n - 1; i++) {
        g[H[i][0]].emplace_back(H[i][1], L[i]);
        g[H[i][1]].emplace_back(H[i][0], L[i]);
    }
    fill(d, d + N, -1);
    build(0, -1, 1, n);

    return (ans == 1e9 ? -1 : ans);
}

• Subtask 1: 0 / 9
• Subtask 2: 0 / 12
• Subtask 3: 0 / 22
• Subtask 4: 0 / 57