Submission #1026126

#	Time	Username	Problem	Language	Result	Execution time	Memory
1026126		vanea	Race (IOI11_race)	C++17	21 / 100	3062 ms	40644 KiB

race

#include <bits/stdc++.h>
using namespace std;
using ll = long long;

const int mxN = 2e5+10;
const int mxK = 1e6+10;
const int INF = 1e9+10;
int ans = INF, k, mx;
int d[mxK];

vector<array<int, 2>> adj[mxN];

bool vis[mxN];
int sz[mxN];

void get_sz(int node, int p) {
    sz[node] = 1;
    for(auto [it, w] : adj[node]) {
        if(it == p || vis[it]) continue;
        get_sz(it, node);
        sz[node] += sz[it];
    }
}

int get_c(int node, int p, int n) {
    for(auto [it, w] : adj[node]) {
        if(vis[it] || it == p) continue;
        if(sz[it] * 2 > n) return get_c(it, node, p);
    }
    return node;
}

void get_min(int node, int p, bool filling, int dist, int s, set<int>& st) {
    if(s > k) return ;
    mx = max(mx, s);
    if(filling) {
        if(dist < d[s]) {
            d[s] = dist;
            st.insert(s);
        }
    }
    else {
        ans = min(ans, dist+d[k-s]);
    }
    for(auto [it, w] : adj[node]) {
        if(it == p || vis[it]) continue;
        get_min(it, node, filling, dist+1, s+w, st);
    }
}

void build(int node) {
    get_sz(node, -1);
    int c = get_c(node, -1, sz[node]);
    vis[c] = true;
    set<int> st;
    for(auto [it, w] : adj[c]) {
        if(vis[it]) continue;
        get_min(it, c, 0, 1, w, st);
        get_min(it, c, 1, 1, w, st);
    }
    for(auto it : st) {
        d[it] = INF;
    }
    d[0] = 0;
    for(auto [it, w] : adj[c]) {
        if(vis[it]) continue;
        build(it);
    }
}

int best_path(int n, int K, int h[][2], int l[]) {
    for(int i = 0; i < n-1; i++) {
        adj[h[i][0]].push_back({h[i][1], l[i]});
        adj[h[i][1]].push_back({h[i][0], l[i]});
    }
    fill(d, d+mxK-5, INF);
    d[0] = 0;
    k = K;
    build(0);
    return (ans == INF ? -1 : ans);
}
/*
int main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout << best_path(11, 12, {{0, 1}, {0, 2}, {2, 3}, {3, 4}, {4, 5}, {0, 6},
                      {6, 7}, {6, 8}, {8, 9}, {8, 10}},
                      {3, 4, 5, 4, 6, 3, 2, 5, 6, 7});
}*/

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