Submission #1217319

#	Time	Username	Problem	Language	Result	Execution time	Memory
1217319		Namkhing	Race (IOI11_race)	C++20	100 / 100	233 ms	32640 KiB

race

#include "race.h"
#include <bits/stdc++.h>
using namespace std;

using pii = pair<int, int>;
const int inf = 1e9;

const int MxN = 2e5 + 10;
const int MxL = 1e6 + 10;
int n, k, ans, sz[MxN], cnt[MxL];
bool used[MxN];
vector<int> res2;
vector<pii> res, adj[MxN];

int dfssz(int u, int p) {
    sz[u] = 1;
    for (auto [v, w] : adj[u]) if (v != p && !used[v]) sz[u] += dfssz(v, u);
    return sz[u];
}

int centroid(int u, int p, int n) {
    for (auto [v, w] : adj[u]) if (v != p && !used[v] && sz[v] > n / 2) return centroid(v, u, n);
    return u;
}

void dfs(int u, int p, int d, int l) {
    if (l > k) return;
    ans = min(ans, d + cnt[k - l]);
    res.push_back({l, d});
    res2.push_back(l);
    for (auto [v, w] : adj[u]) if (v != p && !used[v]) dfs(v, u, d + 1, l + w);
}

void decom(int u) {
    u = centroid(u, -1, dfssz(u, -1));
    used[u] = true;
    for (auto [v, w] : adj[u]) {
        if (used[v]) continue;
        dfs(v, u, 1, w);
        for (auto [l, d] : res) cnt[l] = min(cnt[l], d);
        res.clear();
    }
    for (auto l : res2) cnt[l] = n;
    res2.clear();
    for (auto [v, w] : adj[u]) if (!used[v]) decom(v);
}

int best_path(int N, int K, int H[][2], int L[]) {
    n = N, k = K;
    for (int i = 0; i < n - 1; i++) {
        int u = H[i][0];
        int v = H[i][1];
        int w = L[i];
        adj[u].push_back({v, w});
        adj[v].push_back({u, w});
    }
    for (int i = 1; i <= k; i++) cnt[i] = n;
    ans = n;
    decom(0);
    return ans != n ? ans : -1;
}

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