Submission #387923

#	Time	Username	Problem	Language	Result	Execution time	Memory
387923		pure_mem	Race (IOI11_race)	C++14	0 / 100	3088 ms	4940 KiB

race

#include "race.h"
#include <bits/stdc++.h>

#define X first
#define Y second
#define ll long long
#define MP make_pair

using namespace std;

const int MAXN = 2e5 + 12;

int answer, n, k, sz[MAXN], mx[MAXN], block[MAXN];
vector< pair<int, int> > graph[MAXN];
set< pair<ll, int> > stAct;

void dfs_sz(int v, int pr){
	sz[v] = 1, mx[v] = 0;
	for(pair<int, int> to: graph[v]){
		if(to.X != pr && !block[to.X]){
			dfs_sz(to.X, v), sz[v] += sz[to.X];
			if(sz[mx[v]] < sz[to.X])
				mx[v] = to.X;
		}
	}
}

int get_cent(int v){
	int u = v;
	while(sz[v] < sz[mx[u]] * 2)
		u = mx[u];
	return u;
}

void dfs_prep(int v, int pr, ll cost, int dist){
	if(cost > k)
		return;
	auto it = stAct.lower_bound(MP(k - cost + 1, 0));
	if(it != stAct.begin() && prev(it)->X + cost == k)
		answer = min(answer, dist + prev(it)->Y);
	for(pair<int, int> to: graph[v]){
		if(to.X != pr && !block[to.X])
			dfs_prep(to.X, v, cost + to.Y, dist + 1);
	}	
}

void dfs_add(int v, int pr, ll cost, int dist){
    if(cost > k)
		return;
	auto it = stAct.lower_bound(MP(cost + 1, 0));
	if(it != stAct.begin() && prev(it)->X == cost && prev(it)->Y > dist)
		stAct.erase(prev(it)), stAct.insert(MP(cost, dist));
	else if(it == stAct.begin() || prev(it)->X != cost)
		stAct.insert(MP(cost, dist));
	for(pair<int, int> to: graph[v]){
		if(to.X != pr && !block[to.X])
			dfs_add(to.X, v, cost + to.Y, dist + 1);
	}
}

void cent(int v){
	dfs_sz(v, v);
	v = get_cent(v);
	block[v] = 1;
	stAct.clear();
	stAct.insert(MP(0, 0)); 
	for(pair<int, int> to: graph[v]){
		if(!block[to.X])
			dfs_prep(to.X, v, to.Y, 1), dfs_add(to.X, v, to.Y, 1);
	}
	for(pair<int, int> to: graph[v]){
		if(!block[to.X])
			cent(to.X);
	}
}
     
int best_path(int N, int K, int H[][2], int L[]) {
	answer = N + 1, n = N, k = K;
	for(int i = 0;i < n;i++){
		graph[H[i][0] + 1].push_back(MP(H[i][1] + 1, L[i]));
		graph[H[i][1] + 1].push_back(MP(H[i][0] + 1, L[i]));
	}
	cent(1);
	if(answer == N + 1)
		answer = -1;
	return answer;
}

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