Submission #990856

#	Time	Username	Problem	Language	Result	Execution time	Memory
990856		alexdumitru	Race (IOI11_race)	C++17	0 / 100	3066 ms	8540 KiB

race

#include "race.h"
#include <iostream>
#include <vector>

using namespace std;

const int NMAX = 1e5;
const int KMAX = 1e6;

vector<pair<int, int>> g[NMAX];
int w[NMAX];
bool used[NMAX];
int minLength[KMAX + 1];
int Ans;

int get_w(int node, int dad = -1) {
    w[node] = 1;
    for (auto it : g[node]) {
        if (it.first == dad || used[it.first]) continue;
        get_w(it.first, node);
        w[node] += w[it.first];
    }
    return w[node];
}

int get_centroid(int node, int totalW, int dad = -1) {
    for (auto it : g[node]) {
        if (it.first == dad || used[it.first]) continue;
        if (w[it.first] > totalW / 2)
            return get_centroid(it.first, node);
    }
    return node;
}

void dfs_add(int node, int k, int length = 0, int dad = -1, int depth = 0) {
    if (length > k) return;
    minLength[length] = min(minLength[length], depth);

    for (auto it : g[node]) {
        if (it.first == dad || used[it.first]) continue;
        dfs_add(it.first, k, length + it.second, node, depth + 1);
    }
}

void dfs_compute(int node, int k, int length = 0, int dad = -1) {
    if (length > k) return;
    Ans = min(Ans, minLength[length] + minLength[k - length]);

    for (auto it : g[node]) {
        if (it.first == dad || used[it.first]) continue;
        dfs_compute(it.first, k, length + it.second, node);
    }
}

void dfs_clear(int node, int k, int length = 0, int dad = -1) {
    if (length > k) return;
    minLength[length] = NMAX;

    for (auto it : g[node]) {
        if (it.first == dad || used[it.first]) continue;
        dfs_clear(it.first, k, length + it.second, node);
    }
}

void go(int node, int k) {
    int totalW = get_w(node);
    int c = get_centroid(node, totalW);
    used[c] = true;

    dfs_add(c, k);
    dfs_compute(c, k);
    dfs_clear(c, k);

    for (auto it : g[c])
        if (!used[it.first])
            go(it.first, k);
}

int best_path(int N, int K, int H[][2], int L[]) {
    Ans = N;
    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]);
    }

    go(0, K);

    return Ans == N ? -1 : Ans;
}

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