Submission #1053241

#	Time	Username	Problem	Language	Result	Execution time	Memory
1053241		vincentbucourt1	Race (IOI11_race)	C++14	43 / 100	181 ms	74836 KiB

race

#include "race.h"
#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define f first
#define s second

const static int INF = 1e9;
const int MAXN = 200001;

static int N, sumNeed;
static vector<pair<int, int>> adj[MAXN];

static int depth[MAXN], sum[MAXN];
static map<int, int> maps[MAXN];
static int ans = INF;

void dfs (int node = 0, int parent = -1) {
	maps[node][sum[node]] = depth[node];
	for (pair<int, int> nxt : adj[node]) {
		int nodenxt = nxt.f, weightnxt = nxt.s;
		if (nodenxt == parent) continue;

		depth[nodenxt] = depth[node] + 1;
		sum[nodenxt] = sum[node] + weightnxt;

		dfs(nodenxt, node);

		if (maps[nodenxt].size() > maps[node].size()) swap(maps[nodenxt], maps[node]);
		for (pair<ll, ll> elem : maps[nodenxt]) {
			int sumOn = elem.f, depthOn = elem.s;

			int need = -sumOn + 2*sum[node] + sumNeed;
			if (maps[node].find(need) != maps[node].end()) {
				ans = min(ans, maps[node][need] - 2*depth[node] + depthOn);
			}

			if (maps[node].find(sumOn) == maps[node].end()) {
				maps[node][sumOn] = depthOn;
			}
			else {
				maps[node][sumOn] = min(maps[node][sumOn], depthOn);
			}
		}
		maps[nodenxt].clear();
	}
}

int best_path(int N, int K, int H[][2], int L[])
{
	::N = N;
	sumNeed = K;
	for (int i = 0; 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]});
	}

	dfs();

	if (ans == INF) return -1;
	else return ans;
}

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