Submission #44346

#	Time	Username	Problem	Language	Result	Execution time	Memory
44346		shash42	Race (IOI11_race)	C++11	100 / 100	679 ms	30204 KiB

race

#include<iostream>
#include<vector>
#define pb push_back
#define mp make_pair
#define pii pair<int, int>
using namespace std;
vector< pii > adj[200005];
bool rem[200005];
int K, sub[200005], par[200005], nxt;
int arr[1000005], best=1e9, ans=1e9, inf=1e9;
vector< pii > q;
void dfs1(int u)
{
	sub[u]=1;
	for(pii v: adj[u])
	{
		if(v.first!=par[u] && !rem[v.first])
		{
			par[v.first]=u;
			dfs1(v.first);
			sub[u]+=sub[v.first];
		}
	}
}
void dfs2(int u, int cand)
{
	int currsz=sub[cand]-sub[u];
	for(pii v: adj[u])
	{
		if(v.first!=par[u] && !rem[v.first])
		{
			currsz=max(currsz, sub[v.first]);
			dfs2(v.first, cand);
		}
	}
	if(currsz<best)
	{
		nxt=u;
		best=currsz;
	}
}
void dfs3(int u, int w, int l)
{
	if(w>K) return;
	q.pb(mp(w, l));
	for(pii v: adj[u])
	{
		if(v.first!=par[u] && !rem[v.first])
		{
			par[v.first]=u;
			dfs3(v.first, w+v.second, l+1);	
		}
	}
}
void solve(int cent)
{
	vector<int> tnow;
	tnow.pb(0);
	arr[0]=0;
	for(pii v: adj[cent])
	{
		if(!rem[v.first])
		{
			par[v.first]=cent;
			dfs3(v.first, v.second, 1);
		}
		for(int i = 0; i < q.size(); i++)
		{
			int w=q[i].first, l=q[i].second;
			if(w<=K)
				ans=min(ans, arr[K-w]+l);
		}
		for(int i = 0; i < q.size(); i++)
		{
			arr[q[i].first]=min(arr[q[i].first], q[i].second);
			tnow.pb(q[i].first);
		}
		q.clear();
	}
	for(int i = 0; i < tnow.size(); i++)
		arr[tnow[i]]=inf;
	tnow.clear();
}
void cent(int cand)
{
	nxt=0;
	best=inf;
	par[cand]=cand;
	dfs1(cand);
	dfs2(cand, cand);
	solve(nxt);
	rem[nxt]=true;
	for(pii v: adj[nxt])
		if(!rem[v.first])
			cent(v.first);
}
int best_path(int n, int k, int h[][2], int l[])
{
	K=k;
	for(int i = 1; i <= n; i++)
	{
		adj[i].clear();
		rem[i]=false;
	}
	for(int i = 0; i <= k; i++)
		arr[i]=inf;
	for(int i = 0; i < n-1; i++)
	{
		adj[h[i][0]].pb(mp(h[i][1], l[i]));
		adj[h[i][1]].pb(mp(h[i][0], l[i]));
	}
	cent(1);
	if(ans==inf) ans=-1;
	return ans;
}
/*int main()
{
	int arr[][2]={{0, 1}, {1, 2}};
	int lnt[]={1, 1};
	cout << best_path(11, 12, arr, lnt);
}*/

Compilation message (stderr)

race.cpp: In function 'void solve(int)':
race.cpp:67:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for(int i = 0; i < q.size(); i++)
                  ~~^~~~~~~~~~
race.cpp:73:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for(int i = 0; i < q.size(); i++)
                  ~~^~~~~~~~~~
race.cpp:80:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i = 0; i < tnow.size(); i++)
                 ~~^~~~~~~~~~~~~

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