Submission #461470

#	Time	Username	Problem	Language	Result	Execution time	Memory
461470		kiennguyen246	Race (IOI11_race)	C++14	0 / 100	4 ms	4940 KiB

race

/**
 * \author Nguyen Duc Kien
 * \date ./08/2021
 */

///Task name
#define TASK ""

///-------------------------------------------///

#include <bits/stdc++.h>

using namespace std;

const int maxn = 2e5 + 5;
const int maxnn = 1e6 + 5;

int n, k, res;
vector <pair <int, int> > G[maxn];

namespace BF
{
    void DFS(int u, int d, int l, int par = 0)
    {
        if (l > k) return;
        if (l == k && par) res = min(res, d);
        for (auto p : G[u])
        {
            int v = p.first;
            int w = p.second;
            if (v == par) continue;
            DFS(v, d + 1, l + w, u);
        }

    }

    void Main()
    {
        for (int i = 1; i <= n; i ++) DFS(i, 0, 0);
    }
}

namespace Centroid
{
    int sz[maxn], mpath[maxnn];
    bool mk[maxn];

    void DFS_sz(int u, int par = 0)
    {
        sz[u] = 1;
        for (auto p : G[u])
        {
            int v = p.first;
            if (v == par || mk[v]) continue;
            DFS_sz(v, u);
            sz[u] += sz[v];
        }
    }

    void DFS_mpath(int u, int d, long long l, int par, int com)
    {
        if (l > k) return;
        if (com == 0)
        {
            res = min(res, d + mpath[k - l]);
        }
        else if (com == 1)
        {
            mpath[l] = min(mpath[l], d);
        }
        else if (com == -1)
        {
            mpath[l] = 1e9 + 69;
        }
        for (auto p : G[u])
        {
            int v = p.first;
            int w = p.second;
            if (v == par || mk[v]) continue;
            DFS_mpath(v, d + 1, l + w, u, com);
        }
    }

    int GetCentroid(int u, int msz, int par = 0)
    {
        for (auto p : G[u])
        {
            int v = p.first;
            if (v == par || mk[v]) continue;
            if (sz[v] * 2 > sz[u]) return GetCentroid(v, msz, u);
        }
        return u;
    }

    void Centroid(int u)
    {
        DFS_sz(u);
        int cent = GetCentroid(u, sz[u]);
        mk[cent] = 1;
        for (auto p : G[cent])
        {
            int v = p.first;
            int w = p.second;
            if (mk[v]) continue;
            DFS_mpath(v, 1, w, cent, 0);
            DFS_mpath(v, 1, w, cent, 1);
        }
        if (mpath[k]) res = min(res, mpath[k]);
        for (auto p : G[cent])
        {
            int v = p.first;
            int w = p.first;
            if (mk[v]) continue;
            DFS_mpath(v, 1, w, cent, -1);
        }
        for (auto p : G[cent])
        {
            int v = p.first;
            if (mk[v]) continue;
            Centroid(v);
        }
    }

    void Init()
    {
        fill(mpath, mpath + k, 1e9 + 69);
        for (int i = 1; i <= n; i ++) mk[i] = 0;
        res = 1e9 + 69;
    }
}

int best_path(int __n, int __k, int __h[][2], int __l[])
{
    n = __n, k = __k;
    for (int i = 1; i <= n; i ++) G[i].clear();
    for (int i = 1; i < n; i ++)
    {
        int u = __h[i][0] + 1;
        int v = __h[i][1] + 1;
        int w = __l[i];
        G[u].push_back({v, w});
        G[v].push_back({u, w});
    }
    Centroid::Init();
    Centroid::Centroid(1);
//    BF::Main();
    return (res == 1e9 + 69 ? -1 : res);

}

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