Submission #1090127

#	Time	Username	Problem	Language	Result	Execution time	Memory
1090127		LilPluton	Race (IOI11_race)	C++14	100 / 100	386 ms	86128 KiB

race

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

const int sz = 2e5 + 5;
int n, k;
vector<vector<pair<int, int>>> adj(sz);
map<int, int> a[sz];
long long sum[sz], dep[sz], res;

void comp(int u, int p, long long  c, int h) {
	a[u][c] = h;
	sum[u] = c;
	dep[u] = h;
	for (auto n : adj[u]) {
		if (p == n.first) { continue; }
		comp(n.first, u, c + n.second, h + 1);
	}
}

void dfs(int u, int p) {
    long long target = k + 2 * sum[u];
	for (auto n : adj[u]) {
		if (n.first == p) { continue; }
		dfs(n.first, u);
		if (a[n.first].size() > a[u].size()) { swap(a[n.first], a[u]); }
		for (auto i : a[n.first]) {
			if (a[u].find(target - i.first) != a[u].end()) {
				res = min(res, a[u][target - i.first] + i.second - 2 * dep[u]);
			}
		}
		for (auto i : a[n.first]) {
			if (a[u].find(i.first) == a[u].end()) {
				a[u].insert(i);
			} else {
				a[u][i.first] = min(a[u][i.first], i.second);
			}
		}
	}
}

int best_path(int N, int K, int H[][2], int L[]) {
	if (k == 1) { return 0; }
	n = N;
	k = K;
	res = INT_MAX;
	for (int i = 0; i < n - 1; i++) {
		int u = H[i][0];
		int v = H[i][1];
		adj[u].push_back(pair<int,int> (v, L[i]));
		adj[v].push_back(pair<int,int> (u, L[i]));
	}
	comp(0, -1, 0, 0);
	dfs(0, -1);
	return res == INT_MAX ? -1 : res;
}

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