Submission #1113059

#	Time	Username	Problem	Language	Result	Execution time	Memory
1113059		Matkap	Race (IOI11_race)	C++17	100 / 100	286 ms	38648 KiB

race

/*
    Author:Matkap(prefix_sum)
*/
#include "race.h"
#include <bits/stdc++.h>
#include <array>

using namespace std;
#define endl "\n"
#define ar array
#define all(x) x.begin(),x.end()
const int INF = 1e9 + 7 , MOD = 1e9 + 7;

const int mxN = 2e5 + 7, mxK = 2e6 + 7;
vector<ar<int,2>> adj[mxN];
int rem[mxN];
int sub[mxN];
int cnt[mxK];
int ans = INF;
int k1;
vector<int> vec;
int find_subtree_size(int pos,int par = -1)
{
    sub[pos] = 1;
    for(auto [it, dist] : adj[pos])
    {
        if(it == par || rem[it]) continue;
        sub[pos] += find_subtree_size(it, pos);
    }
    return sub[pos];
}
int find_centroid(int sub_size, int pos,int par = -1)
{
    for(auto [it, dist] : adj[pos])
    {
        if(it == par || rem[it]) continue;
        if(sub[it] > sub_size / 2) return find_centroid(sub_size, it, pos);
    }
    return pos;
}
void solve(int pos,int par,int cur_path,int mode, int depth = 1)
{
    if(cur_path > k1) return;
    if(mode == 1) cnt[cur_path] = min(cnt[cur_path], depth), vec.push_back(cur_path);
    else ans = min(ans, cnt[k1 - cur_path] + depth);
    for(auto [it, dist] : adj[pos])
    {
        if(rem[it] || it == par) continue;
        solve(it,pos,cur_path + dist,mode,depth + 1);
    }
}
void build_decomp(int pos)
{
    int centroid = find_centroid(find_subtree_size(pos), pos);
    //cout << centroid << endl;
    rem[centroid] = 1;
    vec.clear();
    for(auto [it, dist] : adj[centroid])
    {
        if(!rem[it])
        {
            solve(it,-1,dist,0);
            solve(it,-1,dist,1);
        }
    }
    for(auto it : vec) cnt[it] = INF;
    cnt[0] = 0;
    for(auto [it, dist] : adj[centroid])
    {
        if(rem[it]) continue;
        build_decomp(it);
    }
}
int best_path(int n,int k, int h[][2], int l[])
{
    k1 = k;
    fill(cnt, cnt + mxK, INF);
    cnt[0] = 0;
    for(int i = 0;n - 1 > i;i++)
    {
        adj[h[i][0]].push_back({h[i][1], l[i]});
        adj[h[i][1]].push_back({h[i][0], l[i]});
    }
    build_decomp(0);
    if(ans == INF) return -1;
    return ans;
}
/*int32_t main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    int h[1000][2];
    int l[1000];
    int n;
    int k;
    cin >> n >> k;
    for(int i = 0;n - 1 > i;i++) for(int j = 0;2 > j;j++) cin >> h[i][j];
    for(int i = 0;n - 1 > i;i++) cin >> l[i];
    cout << best_path(n, k, h, l) << endl;

}*/

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