Submission #1205078

#	Time	Username	Problem	Language	Result	Execution time	Memory
1205078		nicolo_010	Race (IOI11_race)	C++20	43 / 100	3093 ms	31428 KiB

race

#include <bits/stdc++.h>
#include "race.h"
using namespace std;
template <typename T>
using v = vector<T>;
using ll = long long;
using pii = pair<int, int>;
#define rep(i, k, n) for (int i = k; i < n; i++)
const int mxK = 1e6+1;

v<bool> removed;
v<v<pii>> adj;
v<int> sz;
int a[mxK];
v<pair<int, int>> L;
int ans;
int k;

int dfs(int n, int p) {
    sz[n] = 1;
    for (auto x : adj[n]) {
        if (x.first == p || removed[x.first]) continue;
        sz[n] += dfs(x.first, n);
    }
    return sz[n];
}

int centroid(int u, int p, int n) {
    for (auto x : adj[u]) {
        if (x.first == p || removed[x.first]) continue;
        else if (sz[x.first]*2 >n) return centroid(x.first, u, n);
    }
    return u;
}

void dfs1(int n, int p, int w, int d) {
    L.push_back({w, d});
    for (auto x : adj[n]) {
        if (x.first == p || removed[x.first]) continue;
        if (w+x.second > k) continue;
        dfs1(x.first, n, w+x.second, d+1);
    }
}

void build(int u, int p) {
    int n = dfs(u, p);
    int c = centroid(u, p, n);
    rep(i, 0, k+1) {
        a[i] = -1;
    }
    a[0] = 0;
    for (auto x : adj[c]) {
        if (x.first == p || removed[x.first]) continue;
        L.clear();
        dfs1(x.first, c, x.second, 1);
        for (auto y : L) {
            if (y.first > k) continue;
            if (a[k-y.first] != -1) {
                ans = min(ans, y.second + a[k-y.first]);
            }
        }
        for (auto y : L) {
            if (a[y.first] == -1) a[y.first] = y.second;
            else a[y.first] = min(a[y.first], y.second);
        }
    }
    removed[c] = true;
    for (auto x : adj[c]) {
        if (removed[x.first] || x.first == p) continue;
        build(x.first, c);
    }
}

int best_path(int N, int K, int H[][2], int L[]) {
    int n = N;
    k = K;
    adj.resize(n);
    removed.assign(n, false);
    sz.resize(n);
    rep(i, 0, n-1) {
        adj[H[i][0]].push_back({H[i][1], L[i]});
        adj[H[i][1]].push_back({H[i][0], L[i]});
    }
    ans = 1e9;
    build(0, -1);
    return (ans == 1e9 ? -1 : ans);
}

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