Submission #1231195

#	Time	Username	Problem	Language	Result	Execution time	Memory
1231195		domi	Race (IOI11_race)	C++20	100 / 100	542 ms	31116 KiB

race

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

// #define int long long
// #define fi first
// #define se second
//
// #define sz(a) (int)((a).size())
// #define all(a) (a).begin(), (a).end()
//
// #define lsb(x) (x & (-x))
// #define vi vector<int>
// #define YES { cout << "YES" << endl; return; }
// #define NO { cout << "NO" << endl; return; }
//
// using ll = long long;
// using pii = std::pair<int, int>;

const int NMAX = 2e5;
const int KMAX = 1e6;

using namespace std;

vector<pair<int, int>> T[NMAX + 5];
int sz[NMAX + 5], used[NMAX + 5], best[KMAX + 5], n, k, ans;

void prec_sz(int nod, int p = -1) {
    sz[nod] = 1;
    for (auto &[son, cost] : T[nod]) {
        if (son == p || used[son]) continue;
        prec_sz(son, nod);
        sz[nod] += sz[son];
    }
}

int get_centroid(int nod, int p, int total) {
    for (auto &[son, cost] : T[nod]) {
        if (son == p || used[son]) continue;
        if (sz[son] > total / 2)
            return get_centroid(son, nod, total);
    }
    return nod;
}

void update(int nod, int p, int sum, int depth) {
    if (sum > k) return;
    best[sum] = min(best[sum], depth);
    for (auto &[son, cost] : T[nod]) {
        if (son == p || used[son]) continue;
        update(son, nod, sum + cost, depth + 1);
    }
}

void remove(int nod, int p, int sum, int depth) {
    if (sum > k) return;
    best[sum] = INT_MAX;
    for (auto &[son, cost] : T[nod]) {
        if (son == p || used[son]) continue;
        remove(son, nod, sum + cost, depth + 1);
    }
}

void query(int nod, int p, int sum, int depth) {
    if (sum > k) return;
    if (best[k - sum] != INT_MAX)
        ans = min(ans, best[k - sum] + depth);
    for (auto &[son, cost] : T[nod]) {
        if (son == p || used[son]) continue;
        query(son, nod, sum + cost, depth + 1);
    }
}

void solve(int nod) {
    prec_sz(nod);
    int centroid = get_centroid(nod, -1, sz[nod]);
    used[centroid] = true;

    best[0] = 0;

    for (auto &[son, cost] : T[centroid]) {
        if (used[son]) continue;
        query(son, centroid, cost, 1);
        update(son, centroid, cost, 1);
    }

    for (auto &[son, cost] : T[centroid]) {
        if (used[son]) continue;
        remove(son, centroid, cost, 1);
    }

    for (auto &[son, cost] : T[centroid]) {
        if (!used[son])
            solve(son);
    }
}

int best_path(int N, int K, int H[][2], int L[]) {
    n = N, k = K;
    ans = INT_MAX;

    for (int i = 0; i < n; i++) {
        T[i].clear();
        used[i] = 0;
    }

    for (int i = 0; i <= k; i++) best[i] = INT_MAX;

    for (int i = 0; i < n - 1; i++) {
        int u = H[i][0], v = H[i][1], w = L[i];
        T[u].emplace_back(v, w);
        T[v].emplace_back(u, w);
    }

    solve(0);
    return (ans == INT_MAX ? -1 : ans);
}

// signed main() {
//     cin.tie(nullptr)->sync_with_stdio(false);
//
//     int N, K;
//     cin >> N >> K;
//
//     int H[NMAX][2];
//     int L[NMAX];
//
//     for (int i = 0; i < N - 1; i++) {
//         cin >> H[i][0] >> H[i][1] >> L[i];
//     }
//
//     int answer = best_path(N, K, H, L);
//     cout << answer << '\n';
//
//     return 0;
// }

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