Submission #896135

#	Time	Username	Problem	Language	Result	Execution time	Memory
896135		starchan	Race (IOI11_race)	C++17	0 / 100	4 ms	13912 KiB

race

#include "race.h"
#include<bits/stdc++.h>
using namespace std;
#define in pair<int, int>
#define f first
#define s second
#define pb push_back
#define pob pop_back
#define INF (int)1e9
#define MX (int)2e5+5
#define LMX (int)1e6+5
#define fast() ios_base::sync_with_stdio(false); cin.tie(NULL)
int n, k;
vector<in> adj[MX];
int sz[MX];
bool cut[MX];

void calc_subtree(int u, int p)
{
	sz[u] = 1;
	for(auto [v, w]: adj[u])
	{
		if(v==p)
			continue;
		if(cut[v])
			continue;
		calc_subtree(v, u);
		sz[u]+=sz[v];
	}
	return;
}

int centroid(int root, int u, int p)
{
	for(auto [v, w]: adj[u])
	{
		if(cut[v])
			continue;
		if(v==p)
			continue;
		if(2*sz[v] > sz[root])
			return centroid(root, v, u);
	}
	return u;
}
vector<int> curr;
vector<int> on;
vector<int> best(LMX, INF);
int ans = INF;
void ritul(int u, int p, int lvl, int dist)
{
	if(dist > k)
		return;
	ans = min(ans, lvl+best[k-dist]);
	for(auto [v, w]: adj[u])
	{
		if(v==p)
			continue;
		if(cut[v])
			continue;
		if((dist+w) > k)
			continue;
		ritul(v, u, lvl+1, dist+w);
	}
	return;
}

void ritul2(int u, int p, int lvl, int dist)
{
	if(dist > k)
		return;
	curr.pb(dist);
	best[dist] = min(best[dist], lvl);
	for(auto [v, w]: adj[u])
	{
		if(v==p)
			continue;
		if(cut[v])
			continue;
		if((dist+w) > k)
			continue;
		ritul2(v, u, lvl+1, dist+w);
	}
	return;
}

void centroid_decomp(int u)
{
	calc_subtree(u, -1);
	int root = centroid(u, u, -1);
	cut[root] = 1;
	curr.clear();
	for(auto [v, w]: adj[root])
	{
		if(cut[v])
			continue;
		ritul(v, root, 1, w);
		ritul2(v, root, 1, w);
	}
	for(int t: curr)
		best[t] = INF;
	for(auto [v, w]: adj[root])
	{
		if(cut[v])
			continue;
		centroid_decomp(v);
	}
	return;
}

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];
		int v = h[i][1];
		u++;
		v++;
		int l = L[i];
		adj[u].pb({v, l});
		adj[v].pb({u, l});
	}
	centroid_decomp(1);
	if(ans == INF)
		ans = -1;
	return ans;
}

/*
signed main()
{
	int V, KK;
	cin >> V >> KK;
	int h[V-1][2];	
	int L[V-1];
	for(int i = 0; i < V-1; i++)
		cin >> h[i][0] >> h[i][1] >> L[i];
	int ok = best_path(V, KK, h, L);
	cout << ok << endl; 
	return 0;
}
*/

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