Submission #108743

#	Time	Username	Problem	Language	Result	Execution time	Memory
108743		turbat	Race (IOI11_race)	C++14	43 / 100	3037 ms	36296 KiB

race

#include <bits/stdc++.h>
#include "race.h"
using namespace std;
using vi = vector <int>;
using pii = pair <int, int>;
#define pb push_back
#define F first
#define S second
#define N 200005

int n, k, ans = N, sz[N], mx[N], centroid;
map <int, int> dist;
bool used[N];
vector <pii> edg[N];

void get_size(int u, int p){
	sz[u] = 1;
	mx[u] = 0;
	for (pii v : edg[u])
		if (v.F != p && !used[v.F]){
			get_size(v.F, u);
			mx[u] = max(mx[u], sz[v.F]);
			sz[u] += sz[v.F];
		}
	mx[u] = max(mx[u], n - sz[u]);
}

void get_centroid(int u, int p){
	for (pii v : edg[u])
		if (v.F != p && !used[v.F])
			get_centroid(v.F, u);
	if (mx[u] <= (n + 1) / 2) centroid = u;
}

void calc(int u, int p, int lenght, int distance){
	if(distance > k) return;
	for (pii v : edg[u])
		if (v.F != p && !used[v.F])
			calc(v.F, u, lenght + 1, distance + v.S);
	if (dist.count(k - distance))
		ans = min (ans, lenght + dist[k - distance]);
}

void add(int u, int p, int lenght, int distance){
	if(distance > k) return;
	for (pii v : edg[u])
		if (v.F != p && !used[v.F])
			add(v.F, u, lenght + 1, distance + v.S);
	if (!dist.count(distance)) dist[distance] = lenght;
	else dist[distance] = min(dist[distance], lenght); 
}

void solve(int u){
	dist.clear();
	dist[0] = 0;
	get_size(u, -1);
	n = sz[u];
	get_centroid(u, -1);
	used[centroid] = 1;
	for (pii v : edg[centroid])
		if (!used[v.F]){
			calc(v.F, centroid, 1, v.S);
			add(v.F, centroid, 1, v.S);
		}
	for (pii v : edg[centroid])
		if (!used[v.F])
			solve(v.F);
}

int best_path(int s, int K, int H[][2], int L[]){
	n = s;
	k = K;
	for (int i = 0;i < n - 1;i++){
		edg[H[i][0]].pb({H[i][1], L[i]});
		edg[H[i][1]].pb({H[i][0], L[i]});		
	}
	solve(0);
	return ans == N ? -1 : ans;
}

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