Submission #943365

#	Time	Username	Problem	Language	Result	Execution time	Memory
943365		THXuan	Race (IOI11_race)	C++14	9 / 100	1091 ms	54092 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;
int ans = INF;
vector<pair<int, int>>adj[200005];
bool visited[200005];
ll dp[200005];
vector<int>v;
vector<int>cnt(1e6 + 5, 1e9);

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, ll sum, int dep = 1) {
	if (sum > k) return;
	for (auto u : adj[s]) {
		if (u.first == e || visited[u.first]) continue;
		dfs(u.first, s, flag, sum + u.second, dep + 1);
	}
	if (!flag) {
		ll need = k - sum;
		if (cnt[need] != 1e9) {
			ans = min(ans, dep + cnt[need]);
		}
	}
	else {
		cnt[sum] = min(cnt[sum], dep);
		v.push_back(sum);
	}
}

void centroid_decomposition(int node) {
	int centroid = get_centroid(node, 0, get_size(node, 0));
	visited[centroid] = true;
	cnt[0] = 0;
	for (pair<int,int> u : adj[centroid]) {
		if (!visited[u.first]) {
			dfs(u.first, centroid, false, u.second);
			dfs(u.first, centroid, true, u.second);
		}
	}
	for (auto u : v) cnt[u] = INF;
	v.clear();
	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++) {
		int u = h[i][0], v = h[i][1], w = l[i];
		adj[u].push_back({ v, w });
		adj[v].push_back({ u, w });
	}
	centroid_decomposition(1);
	if (ans == 1e9) return -1;
	else return ans;
}

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