Submission #150039

#	Time	Username	Problem	Language	Result	Execution time	Memory
150039		ummm (#200)	Trip to the Galapagos Islands (FXCUP4_island)	C++17	31 / 100	4627 ms	489316 KiB

island

#include "island.h"

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

const int GAP = 500;

struct UnionFind {
	int n;
	vector<int> uf,si,c;
	UnionFind(int n=0):n(n),uf(n),si(n,1){
		for(int i=0;i<n;++i) 
			uf[i]=i;
	}
	int find(int x){return x==uf[x]?x:find(uf[x]);}
	bool join(int x, int y, bool keep_track){
		if((x=find(x))==(y=find(y))) return false;
		if(si[x]<si[y]) swap(x,y);
		// cout << "Joining " << x << ' ' << y << '\n';
		si[x]+=si[y];uf[y]=x;
		if(keep_track) c.push_back(y);
		return true;
	}
	void rollback(){
		while(c.size()){
			int x=c.back(); c.pop_back();
			si[uf[x]]-=si[x];uf[x]=x;;
		}
	}
} UF[605];

vector<pair<int,int>> edges;
vector<int> F;
vector<int> pos[100005];

int M, N;

void Init(int K, vector<int> F, vector<int> S, vector<int> E){
	N = F.size();
	M = S.size();
	edges.resize(M);
	for(int i=0;i<M;++i)
		edges[i] = make_pair(S[i], E[i]);
	reverse(edges.begin(), edges.end());

	for(int i=0;i<(int)F.size();++i)
		pos[F[i]].push_back(i);

	UnionFind cur(N);

	::F = F;

	for(int i=0;i<M;++i){
		if(i%GAP==0) UF[i/GAP] = cur;
		cur.join(edges[i].first, edges[i].second, 0);
	}
}

map<int,int> memo[100005];
int Separate(int A, int B){
	if(A>B) swap(A,B);
	if(memo[A].count(B)) return memo[A][B];

	int bucket = 0, start = 0, ans = -1;
	for(int i=0;i<M;i+=GAP){
		if(UF[i/GAP].find(pos[A][0]) == UF[i/GAP].find(pos[B][0]))
			break;
		start = i, bucket = i/GAP;
	}
	for(auto i:pos[A]) {
		// cout << i << ' ' << pos[A][0] << '\n';
		UF[bucket].join(pos[A][0],i, 1);
	}
	for(auto i:pos[B]) {
		// cout << i << ' ' << pos[B][0] << '\n';
		UF[bucket].join(pos[B][0],i, 1);
	}

	for(int i=start;i<start+GAP && i<M; ++i){
		// cout << edges[i].first << ' ' <<edges[i].second << '\n';
		UF[bucket].join(edges[i].first, edges[i].second, 1);
		if(UF[bucket].find(pos[A][0]) == UF[bucket].find(pos[B][0])){
			ans = M - i;
			break;
		}
	}
	assert(ans != -1);
	UF[bucket].rollback();
	return memo[A][B] = ans;
}

• Subtask 1: 31 / 31
• Subtask 2: 0 / 39
• Subtask 3: 0 / 30