Submission #422198

#	Time	Username	Problem	Language	Result	Execution time	Memory
422198		ScarletS	Race (IOI11_race)	C++17	21 / 100	3063 ms	12356 KiB

race

#include <bits/stdc++.h>
using namespace std;

const int N = 1<<18, INF = 1e9;
int k, x, y, ans = INF, dp[1<<20], sub[N];
array<int,2> a[N];
vector<array<int,2>> e[N];
bitset<N> b;

void subDfs(int c, int p)
{
	sub[c]=1;
	for (auto i : e[c])
		if (i[0]!=p&&!b[i[0]])
		{
			subDfs(i[0],c);
			sub[c]+=sub[i[0]];
		}
}

int findC(int c, int p, int t)
{
	for (auto i : e[c])
		if (i[0]!=p&&!b[i[0]]&&sub[i[0]]>t)
			return findC(i[0],c,t);
	return c;
}

void dfs(int c, int p, int h, int t)
{
	if (h>k)
		return;
	a[x++]={h,t};
	ans=min(ans,dp[k-h]+t);
	for (auto i : e[c])
		if (i[0]!=p)
			dfs(i[0],c,h+i[1],t+1);
}

void solve(int n)
{
	subDfs(n,-1);
	int c = findC(n,-1,sub[n]/2);
	b[c]=1;
	x=0;
	for (auto i : e[c])
		if (!b[i[0]])
		{
			y=x;
			dfs(i[0],c,i[1],1);
			for (int j=y;j<x;++j)
				dp[a[j][0]]=min(dp[a[j][0]],a[j][1]);
		}
	for (int i=0;i<x;++i)
		dp[a[i][0]]=INF;
	for (auto i : e[c])
		if (!b[i[0]])
			solve(i[0]);
}

int best_path(int n, int K, int h[][2], int l[])
{
	k=K;
	for (int i=0;i<n-1;++i)
	{
		e[h[i][0]].push_back({h[i][1],l[i]});
		e[h[i][1]].push_back({h[i][0],l[i]});
	}
	for (int i=1;i<=k;++i)
		dp[i]=INF;
	solve(0);
	if (ans==INF)
		return -1;
	return ans;
}

// int main()
// {
// 	int n,k;
// 	cin>>n>>k;
// 	int h[n-1][2], l[n-1];
// 	for (int i=0;i+1<n;++i)
// 		cin>>h[i][0]>>h[i][1]>>l[i];
// 	cout<<best_path(n,k,h,l);
// 	return 0;
// }

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