Submission #238704

#	Time	Username	Problem	Language	Result	Execution time	Memory
238704		T0p_	Race (IOI11_race)	C++14	0 / 100	15 ms	19328 KiB

race

#include "race.h"
#include <bits/stdc++.h>
using namespace std;
 
#define N 200002
#define pb push_back
 
struct EDGE
{
	int node, weight;
};
 
int ans = 1e9, K;
int lv[N], jmp[2][20][N], sz[N];
bool visit[N];
map<int, int> mp[N];
vector<int> gc[N];
vector<EDGE> g[N];
queue<pair<int, int>> q;
 
void dfs1(int u, int l)
{
	lv[u] = l;
	for(auto x : g[u])
	{
		if(lv[x.node]) continue ;
		dfs1(x.node, l+1);
		jmp[0][0][x.node] = u;
		jmp[1][0][x.node] = x.weight;
	}
}
 
int get_sz(int u, int p)
{
	sz[u] = 1;
	for(auto x : g[u])
	{
		if(visit[x.node] || x.node == p) continue ;
		sz[u] += get_sz(x.node, u);
	}
	return sz[u];
}
 
int get_centroid(int u, int p, int n)
{
	bool ch = (n - sz[u] <= n/2) ? true : false;
	int nn = 0, nf = 0;
	for(auto x : g[u])
	{
		if(visit[x.node] || x.node == p) continue ;
		if(sz[x.node] > n/2)
		{
			ch = false;
			if(sz[x.node] > nf)
			{
				nn = x.node;
				nf = sz[x.node];
			}
		}
	}
	return (ch) ? u : get_centroid(nn, u, n);
}
 
pair<int, int> finddis(int u, int v)
{
	int r1 = 0, r2 = 0;
	if(lv[u] < lv[v]) swap(u, v);
	for(int i=19 ; i>=0 ; i--)
		if(lv[jmp[0][i][u]] >= lv[v])
		{
			r1 += (1<<i);
			r2 += jmp[1][i][u];
			u = jmp[0][i][u];
		}
	if(u == v) return {r1, r2};
	for(int i=19 ; i>=0 ; i--)
		if(jmp[0][i][u] != jmp[0][i][v])
		{
			r1 += (1<<(i+1));
			r2 += jmp[1][i][u] + jmp[1][i][v];
			u = jmp[0][i][u], v = jmp[0][i][v];
		}
	return {r1+2, r2+jmp[1][0][u]+jmp[1][0][v]};
}
 
int build(int u, int p)
{
	int c = get_centroid(u, p, get_sz(u, p));
	visit[c] = true;
	for(auto x : g[c])
	{
		if(visit[x.node]) continue ;
		gc[c].pb(build(x.node, c));
	}
	return c;
 
}
 
void compute(int u, int p)
{
	pair<int, int> dis = finddis(u, p);
	if(mp[p].count(K - dis.second)) ans = min(ans, mp[p][K-dis.second] + dis.first);
	q.push(dis);
	for(auto x : gc[u]) compute(x, p);
}
 
void dfs2(int u)
{
	mp[u][0] = 0;
	for(auto x : gc[u])
	{
		compute(x, u);
		while(!q.empty())
		{
			int f = q.front().first, s = q.front().second;
			q.pop();
			if(mp[u].count(f)) mp[u][f] = min(mp[u][f], s);
			else mp[u][f] = s;
		}
	}
	mp[u].clear();
	for(auto x : gc[u])
		dfs2(x);
 
}
 
int best_path(int n, int k, int h[][2], int l[])
{
	K = k;
	for(int i=0 ; i<n-1 ; i++)
	{
		g[h[i][0]+1].pb({h[i][1]+1, l[i]});
		g[h[i][1]+1].pb({h[i][0]+1, l[i]});
	}
	dfs1(1, 1);
	for(int i=1 ; i<20 ; i++)
		for(int j=1 ; j<=n ; j++)
		{
			jmp[0][i][j] = jmp[0][i-1][jmp[0][i-1][j]];
			jmp[1][i][j] = jmp[1][i-1][j] + jmp[1][i-1][jmp[0][i-1][j]];
		}
	dfs2(build(1, 0));
	return (ans == 1e9) ? -1 : ans;
}

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