제출 #648261

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
648261		smirichto	경주 (Race) (IOI11_race)	C++17	100 / 100	477 ms	106444 KiB

race

#include <bits/stdc++.h>

using namespace std;

typedef long long ll;
typedef pair<ll, ll> pii;

#define pb push_back

#define f first
#define s second

const int maxn = 2e5 + 1;
vector<pii> adj[maxn];
map<ll, ll> info[maxn];
ll dist[maxn], sum[maxn];  // define these relative to root
int N, K;
ll ret;

void precomp(int u, int p, ll c, int h)
{
	info[u][c] = h;
	sum[u] = c;
	dist[u] = h;
	for (auto n : adj[u])
	{
		if (p == n.f)
		{
			continue;
		}
		precomp(n.f, u, c + n.s, h + 1);
	}
}

void small_to_large_merge(int u, int p)
{
	ll target = K + 2 * sum[u];
	for (auto n : adj[u])
	{
		if (n.f == p)
		{
			continue;
		}
		small_to_large_merge(n.f, u);
		if (info[n.f].size() > info[u].size())
		{
			swap(info[n.f], info[u]);
		}
		for (auto i : info[n.f])
		{
			if (info[u].find(target - i.f) != info[u].end())
			{
				ret = min(ret, info[u][target - i.f] + i.s - 2 * dist[u]);
			}
		}
		for (auto i : info[n.f])
		{
			if (info[u].find(i.f) == info[u].end())
			{
				info[u].insert(i);
			}
			else
			{
				info[u][i.f] = min(info[u][i.f], i.s);
			}
		}
	}
}

int best_path(int n, int k, int edges[][2], int weights[])
{
	if (k == 1)
	{
		return 0;
	}
	N = n;
	K = k;
	ret = INT_MAX;
	for (int i = 0; i < n - 1; i++)
	{
		int u = edges[i][0];
		int v = edges[i][1];
		adj[u].pb(pii(v, weights[i]));
		adj[v].pb(pii(u, weights[i]));
	}
	precomp(0, -1, 0, 0);
	small_to_large_merge(0, -1);
	return ret == INT_MAX ? -1 : ret;
}

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