Submission #942431

#	Time	Username	Problem	Language	Result	Execution time	Memory
942431		THXuan	Race (IOI11_race)	C++14	9 / 100	3035 ms	25564 KiB

race

#include <iostream>
#include <vector>
#include <algorithm>
#include <cstring>
#include <queue>
#include <set>
#include <map>
#define INF 1e9
using namespace std;
typedef long long ll;

int n, k;
ll ans = INF;
vector<pair<int, int>>adj[200005];
bool visited[200005];
ll dp[200005];
map<ll,ll>seen;
vector<ll>v;

int get_size(int s, int e) {
	dp[s] = 1;
	for (auto u : adj[s]) {
		if (u.first == e || visited[u.first]) continue;
		get_size(u.first, s);
		dp[s] += dp[u.first];
	}
	return dp[s];
}

int get_centroid(int s, int e, int n) {
	for (auto u : adj[s]) {
		if (u.first == e || visited[u.first]) continue;
		if (dp[u.first] * 2 > n)return get_centroid(u.first, s, n);
	}
	return s;
}

void dfs(int s, int e, bool flag, int sum, ll dep = 1) {
	if (!flag) {
		if (seen.find(k - sum) != seen.end()) ans = min(ans, seen[k - sum] + dep);
	}
	else {
		if (seen.find(sum) == seen.end())seen[sum] = dep;
		else seen[sum] = min(seen[sum], dep);
	}
	for (auto u : adj[s]) {
		if (u.first == e || visited[u.first]) continue;
		dfs(u.first, s, flag, sum + u.second, dep + 1);
	}
}

void centroid_decomposition(int node) {
	int centroid = get_centroid(node, 0, get_size(node, 0));
	visited[centroid] = true;
	seen.clear();
	for (auto u : adj[centroid]) {
		if (!visited[u.first]) {
			dfs(u.first, centroid, false, u.second);
			dfs(u.first, centroid, true, u.second);
		}
	}
	if (seen.find(k) != seen.end()) ans = min(ans, seen[k]);
	for (auto u : adj[centroid]) {
		if (!visited[u.first])centroid_decomposition(u.first);
	}
}

int best_path(int N, int K, int H[][2], int L[]) {
	n = N; k = K;
	for (int i = 1; i <= N - 1; i++) {
		adj[H[i][0]].push_back({ H[i][1],L[i] });
		adj[H[i][1]].push_back({ H[i][0],L[i] });
	}
	centroid_decomposition(1);
	if (ans == INF) return -1;
	return ans;
}

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