제출 #1236708

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
1236708		nerrrmin	Race (IOI11_race)	C++20	100 / 100	266 ms	76000 KiB

race

#include "race.h"
#include<bits/stdc++.h>
#define pb push_back
using namespace std;
const int maxn = 2e6 + 10;
int n, k;
vector < pair< int, int > > g[maxn];

int block[maxn], all, half, sz[maxn];
void calc(int beg, int from)
{
    //cout << "calc " << beg << " " << from << endl;
    sz[beg] = 1;
    for (auto &[nb, w]: g[beg])
    {
       // cout << "nb? " << nb << endl;
        if(nb == from || block[nb])continue;
        calc(nb, beg);
        sz[beg] += sz[nb];
    }
}
int find_centroid(int beg, int from)
{
    for (auto &[nb, w]: g[beg])
    {
        if(nb == from || block[nb])continue;
        if(sz[nb] > half)return find_centroid(nb, beg);
    }
    return beg;
}
vector < pair < int, int > > p;
int ans;
int mp[maxn];
vector < int > rem;
void dfs(int beg, int from, int cnt, int w)
{
    if(w > k)return;
    if(w == k)
    {
        ans = min(ans, cnt);
        return;
    }
    else
    {
        int curr = cnt + mp[k - w];
        ans = min(ans, curr);
    }

    p.pb({w, cnt});
    for (auto &[nb, ww]: g[beg])
    {
        if(nb == from || block[nb])continue;
        dfs(nb, beg, cnt + 1, w + ww);
    }
}
void decompose(int v, int from)
{
   // cout << "decomposing "<< v << endl;
    calc(v, -1);
    all = sz[v];
    half = all/2;
    int nc = find_centroid(v, -1);
    block[nc] = 1;
   // cout << all << " " << half << " " << nc << endl;
    for (auto x: rem)
        mp[x] = n;
    rem.clear();
    for (auto &[nb, w]: g[nc])
    {
        if(block[nb])continue;
        dfs(nb, -1, 1, w);

        for (auto &[value, cnt]: p)
        {
            if(mp[value] == n)rem.pb(value);
            mp[value] = min(mp[value], cnt);
        }
        p.clear();
    }
    for (auto &[nb, w]: g[nc])
    {
        if(block[nb])continue;
        decompose(nb, nc);
    }
}
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], v = H[i][1], w = L[i];
        g[u].pb({v, w});
        g[v].pb({u, w});
    }
    ans = n;
    for (int i = 1; i <= 2*k; ++ i)
        mp[i] = n;
    decompose(1, -1);

    if(ans == n)return -1; //cout << ans << endl;
  return ans;
}
/**
11 12
0 1 3
0 2 4
2 3 5
3 4 4
4 5 6
0 6 3
6 7 2
6 8 5
8 9 6
8 10 7
2
*/

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