Submission #896093

#	Time	Username	Problem	Language	Result	Execution time	Memory
896093		starchan	Race (IOI11_race)	C++17	0 / 100	3 ms	18780 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)1e17
#define MX (int)2e5+5
#define fast() ios_base::sync_with_stdio(false); cin.tie(NULL)
int n, k;
vector<in> adj[MX];
int sz[MX]; 

vector<bool> cut;
void dfs1(int u, int p)
{
	sz[u] = 1;
	for(in vw: adj[u])
	{
		int v = vw.f;
		if(cut[v])
			continue;
		if(v == p)
			continue;
		dfs1(v, u);
		sz[u]+=sz[v];
	}
	return;
}
vector<in> comp[MX];
vector<int> centr[MX];
int centroid(int root, int u, int p)
{
	for(in vw: adj[u])
	{
		int v = vw.f;
		if(cut[v])
			continue;
		if(v==p)
			continue;
		if(2*sz[v] > sz[root])
			return centroid(root, v, u);
	}
	return u;
}
void dfs2(int root, int u, int p, int lvl, int d)
{
	comp[root].pb({d, lvl});
	for(in vw: adj[u])
	{
		int v = vw.f;
		int w = vw.s;
		if(cut[v])
			continue;
		if(v==p)
			continue;
		int cost = d+w;
		if(cost > k)
			cost = k+1;
		dfs2(root, v, u, lvl+1, cost);
	}
	return;
}
int centroid_decomposition(int u)
{
	dfs1(u, -1);
	int root = centroid(u, u, -1);
	cut[root] = 1;
	for(in vw: adj[root])
	{
		int v = vw.f;
		if(cut[v])
			continue;
		dfs2(v, v, root, 1, vw.s);
		centr[root].pb(centroid_decomposition(v));
	}
	return root;
}
int dfs3(int u, int p)
{
	int ans = n+1;
	map<int, int> freq;
	freq[0] = 0;
	for(int v: centr[u])
	{
		ans = min(ans, dfs3(v, u));
		for(in L_edge: comp[v])
		{
			int L = L_edge.f;
			int dep = L_edge.s;
			if(L > k)
				continue;
			if(freq.find(k-L) == freq.end())
				continue;
			ans = min(ans, dep+freq[k-L]);
		}
		for(in L_edge: comp[v])
		{
			int L = L_edge.f;
			int dep = L_edge.s;
			if(freq.find(L) == freq.end())
				freq[L] = dep;
			else
				freq[L] = min(freq[L], dep);
		}
	}
	return ans;
}
int best_path(int N, int K, int h[][2], int L[])
{
	n = N;
	k = K;
	for(int i = 1; i <= n; i++)
		adj[i].clear();
	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});
	}
	cut.assign(n+1, 0);
	int root = centroid_decomposition(1);
	int ans = dfs3(root, -1);
	if(ans == (n+1))
		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