Submission #409981

#	Time	Username	Problem	Language	Result	Execution time	Memory
409981		MohamedAhmed04	Swapping Cities (APIO20_swap)	C++14	6 / 100	558 ms	63528 KiB

swap

#include <bits/stdc++.h>
#include "swap.h"
//#include "grader.cpp"

using namespace std ;

const int inf = 2e9 ;
const int MAX = 1e5 + 10 ;

int par[MAX] , sz[MAX] , cyc[MAX] ;
vector<int>comp[MAX] ;

int n , m ;

void Init()
{
	for(int i = 1 ; i <= n ; ++i)
		cyc[i] = inf , comp[i].push_back(i) , par[i] = i , sz[i] = 1 ;
}

int root(int node)
{
	if(par[node] == node)
		return node ;
	return (par[node] = root(par[node])) ;
}

void Union(int x , int y , int z)
{
	int a = root(x) ;
	int b = root(y) ;
	if(cyc[a] == inf && cyc[b] != inf)
	{
		for(auto &node : comp[a])
			cyc[node] = z ;
	}
	else if(cyc[a] != inf && cyc[b] == inf)
	{
		for(auto &node : comp[b])
			cyc[node] = z ;
	}
	if(sz[a] < sz[b])
		swap(a , b) ;
	while(comp[b].size())
		comp[a].push_back(comp[b].back()) , comp[b].pop_back() ;
	par[b] = a ;
	sz[a] += sz[b] ;	
}

vector< vector< pair<int , int> > >adj(MAX) ;

int arr2[MAX] , arr3[MAX] , Pval[MAX] , Min[MAX] ;
int P[MAX][20] , Max[MAX][20] , val[MAX][20] , dep[MAX] ;

void dfs(int node , int par , int x , int y)
{
	Pval[node] = x ;
	P[node][0] = par ;
	Max[node][0] = x ;
	val[node][0] = y ;
	for(int i = 1 ; i < 17 ; ++i)
	{
		P[node][i] = P[P[node][i-1]][i-1] ;
		Max[node][i] = max(Max[node][i-1] , Max[P[node][i-1]][i-1]) ;
		val[node][i] = min(val[node][i-1] , val[P[node][i-1]][i-1]) ;
	}
	vector<int>v ;
	for(auto &child : adj[node])
	{
		if(child.first == par)
			continue ;
		v.push_back(child.second) ;
	}
	sort(v.begin() , v.end()) ;
	arr2[node] = arr3[node] = Min[node] = inf ;
	if(v.size() > 1)
		arr2[node] = v[1] ;
	if(v.size() > 2)
		arr3[node] = v[2] , Min[node] = v[2] ;
	for(auto &child : adj[node])
	{
		if(child.first == par)
			continue ;
		dep[child.first] = dep[node] + 1 ;
		dfs(child.first , node , child.second , arr2[node]) ;
		Min[node] = min(Min[node] , max(child.second , Min[child.first])) ;
	}
}

int calc(int x , int y)
{
	if(dep[x] < dep[y])
		swap(x , y) ;
	int a = -inf , b = Min[x] ;
	b = min(cyc[x] , cyc[y]) ;
	for(int i = 16 ; i >= 0 ; --i)
	{
		if((dep[x] - (1 << i)) > dep[y])
		{
			a = max(a , Max[x][i]) ;
			b = min(b , val[x][i]) ;
			x = P[x][i] ;
		}
	}
	if(dep[x] != dep[y])
	{
		if(P[x][0] != y)
			b = min(b , val[x][0]) ;
		a = max(a , Max[x][0]) ;
		x = P[x][0] ;
	}
	if(x == y)
		return max(a , min(b , max(arr2[y] , Pval[y]))) ;
	b = min(b , Min[y]) ;
	for(int i = 16 ; i >= 0 ; --i)
	{
		if(P[x][i] != P[y][i])
		{
			a = max(a , max(Max[x][i] , Max[y][i])) ;
			b = min(b , min(val[x][i] , val[y][i])) ;
			x = P[x][i] , y = P[y][i] ;
		}
	}
	a = max(a , max(Max[x][0] , Max[y][0])) ;
	b = min(b , min(arr3[P[x][0]] , Pval[P[x][0]])) ;
	return max(a , b) ;
}

void init(int N, int M,
          std::vector<int> U, std::vector<int> V, std::vector<int> W) {

	n = N , m = M ;
	vector< array<int , 3> >v ;
	for(int i = 0 ; i < m ; ++i)
		v.push_back({W[i] , U[i]+1 , V[i]+1}) ;
	Init() ;
	sort(v.begin() , v.end()) ;
	for(auto &a : v)
	{
		int x = a[1] , y = a[2] , z = a[0] ;
		if(root(x) == root(y))
		{
			int r = root(x) ;
			if(cyc[r] == inf)
			{
				for(auto &node : comp[r])
					cyc[node] = z ;
			}
		}
		else
			Union(x , y , z) , adj[x].emplace_back(y , z) , adj[y].emplace_back(x , z) ;
	}
	dfs(1 , 0 , inf , inf) ;
}

int getMinimumFuelCapacity(int x, int y) 
{
	x++ , y++ ;
	int ans = calc(x , y) ;
	if(ans == inf)
		ans = -1 ;
	return ans ;
}

• Subtask 1: 6 / 6
• Subtask 2: 0 / 7
• Subtask 3: 0 / 17
• Subtask 4: 0 / 20
• Subtask 5: 0 / 23
• Subtask 6: 0 / 27