Submission #1274256

#	Time	Username	Problem	Language	Result	Execution time	Memory
1274256		ademby	Race (IOI11_race)	C++20	0 / 100	1 ms	332 KiB

race

//بسم الله الرحمان الرحيم
//we are the winners
//we are the champions

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>

using namespace std;
using namespace __gnu_pbds;

template<class T>
using ordered_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
template<class T>
using ordered_multiset = tree<T, null_type, less_equal<T>, rb_tree_tag, tree_order_statistics_node_update>;

#define IOS ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
#define pb emplace_back
#define lv (v<<1)
#define rv ((v<<1)|1)
#define endl '\n'

#define rep(i, a, b) for(int i = a; i < (b); ++i)
#define all(x) begin(x), end(x)
#define sz(x) (int)(x).size()
typedef long long ll;
typedef pair<int, int> pii;
typedef vector<int> vi;

struct Centroid_Decomposition {
    /* Internals */
    int n, k, ans;
    const vector<vector<pii>>& adj;
    vector<int> sub_sz, is_centroid, other;

    /* Problem Specific */
    // ...

    /* Initialize the Centroid Decomposition */
    Centroid_Decomposition(int n, int k, const vector<vector<pii>> &g) : n(n), k(k), ans(n), adj(g), sub_sz(n + 10), is_centroid(n + 10), other(k + 10) {}

    /* Update subtree size of each node */
    int updateSize(int u, int p = -1){
        sub_sz[u] = 1;
        for (auto [v, w] : adj[u])
            if (v != p && !is_centroid[v])
                sub_sz[u] += updateSize(v, u);
        return sub_sz[u];
    }

    /* Get centroid of subtree rooted at u */
    int getCentroid(int u, int target, int p = -1){
        for(auto [v, w] : adj[u]){
            if(v == p || is_centroid[v]) continue;
            if((sub_sz[v]>>1) > target)
                return getCentroid(v, target, u);
        }
        return u;
    }

    void update_ans(int u, int p, int dep_cent, int dist_cent) {
        if (dist_cent > k) return;
        int cand = other[k-dist_cent];
        if (cand > 0 || k-dist_cent == 0) ans = min(ans, cand + dep_cent);
        for (auto& [nxt, w] : adj[u]) {
            if(nxt == p || is_centroid[nxt]) continue;
            update_ans(nxt, u, dep_cent+1, dist_cent+w);
        }
    }

    void update_lens(int u, int p, int dep_cent, int dist_cent) {
        if (dist_cent > k) return;
        int& cand = other[dist_cent];
        if (cand > 0) cand = min(cand, dep_cent);
        else {
            cand = dep_cent;
        }
        for (auto& [nxt, w] : adj[u]) {
            if(nxt == p || is_centroid[nxt]) continue;
            update_lens(nxt, u, dep_cent+1, dist_cent+w);
        }
    }
    void delete_lens(int u, int p, int dep_cent, int dist_cent) {
        if (dist_cent > k) return;
        other[dist_cent] = 0;
        for (auto& [nxt, w] : adj[u]) {
            if(nxt == p || is_centroid[nxt]) continue;
            delete_lens(nxt, u, dep_cent+1, dist_cent+w);
        }
    }

    /* Decompose tree into centroid tree */
    void Centroid(int u, int p){
        int cur_sz = updateSize(u);
        int centroidPoint = getCentroid(u, cur_sz);
        is_centroid[centroidPoint] = true;

        // do something with centroid
        for(auto [v, w] : adj[centroidPoint]){
            if(is_centroid[v]) continue;
            update_ans(v, centroidPoint, 1, w);
            update_lens(v, centroidPoint, 1, w);
        }
        for(auto [v, w] : adj[centroidPoint]){
            if(is_centroid[v]) continue;
            delete_lens(v, centroidPoint, 1, w);
        }

        for(auto [v, w] : adj[centroidPoint]){
            if(is_centroid[v]) continue;
            // prepare for a dive
            Centroid(v, centroidPoint);
            // recover
        }

        // do something with centroid
    }

    // Call this function to decompose the tree
    void Decompose(){ Centroid(0, -1); }
};

int best_path(int _n, int _k, int e[][2], int w[]) {
    int n = _n;
    int k = _k;
    int ans = n;
    vector<vector<pii>> adj(n);
    rep(i, 0, n-1) {
        adj[e[i][0]].pb(e[i][1], w[i]);
        adj[e[i][1]].pb(e[i][0], w[i]);
    }
    Centroid_Decomposition cent(n, k, adj);
    cent.Decompose();
    if (ans == n) return -1;
    return ans;
}

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