Submission #1040703

#	Time	Username	Problem	Language	Result	Execution time	Memory
1040703		Dan4Life	Fountain Parks (IOI21_parks)	C++17	15 / 100	126 ms	50840 KiB

parks

#include "parks.h"
#include <bits/stdc++.h>
using namespace std;
#define pb push_back
#define sz(a) (int)a.size()
#define all(a) begin(a),end(a)
using vi = vector<int>;
using ll = long long;
using ar2 = array<int,2>;
using ar3 = array<int,3>;

const int mxN = (int)2e5+10;
int n;
struct Edge{
	int fa, fb, x, y;
	Edge(int a=0, int b=0, int _x=-1, int _y=-1){
		fa=a, fb=b, x=_x, y=_y;
	}
};
vector<Edge> edges;
vector<ar3> fountains;

template<int SZ> struct DSU{
	int p[SZ];
	vector<int> comp[SZ];
	void init(int n){
		for(int i = 0; i < n; i++){
			p[i]=i; comp[i].clear();
			comp[i].pb(i);
		}
	}
	
	int findSet(int i){return p[i]==i?i:p[i]=findSet(p[i]);}
	bool isSameSet(int i, int j) {return findSet(i)==findSet(j);}
	void unionSet(int i, int j){
		int x = findSet(i), y = findSet(j);
		if(x==y) return;
		if(sz(comp[x]) < sz(comp[y])) swap(x,y);
		p[y]=x; for(auto u : comp[y]) comp[x].pb(u);
	}
	int findSz(int i) { return sz(comp[findSet(i)]); }
};
DSU<mxN> dsu;
set<int> usedB;

int construct_roads(vi x, vi y) {
	n = sz(x); dsu.init(n);
	if (n==1){ build({}, {}, {}, {}); return 1; }
	int mnX = *min_element(all(x));
	int mxX = *max_element(all(x));
	for(int i = 0; i < n; i++){
		fountains.pb({x[i],y[i],i});
	}
	
	if(mnX==mxX){
		sort(all(fountains),[&](ar3 a, ar3 b){ return a[1]<b[1]; });
		for(int i = 1; i < sz(fountains); i++){
			if(fountains[i][1]-fountains[i-1][1]==2){
				auto [x1,y1,a] = fountains[i-1];
				auto [x2,y2,b] = fountains[i];
				dsu.unionSet(a,b);
				edges.pb(Edge(a,b,x1-1,y1+1));
			}
		}
	}
	else if(mxX-mnX==2){
		sort(all(fountains),[&](ar3 a, ar3 b){ 
			if(a[0]!=b[0]) return a[0]<b[0];
			return a[1]<b[1]; 
		});
		set<ar2> S; S.clear();
		for(int i = sz(fountains)-1; i>=0; i--){
			if(fountains[i][0]!=mxX) break;
			S.insert({fountains[i][1], fountains[i][2]});
		}
		for(int i = 1; i < sz(fountains); i++){
			if(fountains[i][0]!=fountains[i-1][0]) continue;
			if(fountains[i][1]-fountains[i-1][1]==2){
				auto [x1,y1,a] = fountains[i-1];
				auto [x2,y2,b] = fountains[i];
				dsu.unionSet(a,b);
				if(x1==mnX) edges.pb(Edge(a,b,x1-1,y1+1));
				else edges.pb(Edge(a,b,x1+1,y1+1));
			}
		}
		
		for(int i = 0; i < sz(fountains); i++){
			auto [x1,y1,a] = fountains[i];
			if(x1!=mnX) break;
			auto itr = S.lower_bound({y1,-1});
			if(itr==end(S) or (*itr)[0]!=y1) continue;
			int b = (*itr)[1];
			dsu.unionSet(a,b);
			edges.pb(Edge(a,b,x1+1,y1-1));
		}
	}
	else if(mxX-mnX==4 and 0){ // currently false for now
		sort(all(fountains),[&](ar3 a, ar3 b){ 
			if(a[0]!=b[0]) return a[0]<b[0];
			return a[1]<b[1]; 
		});
	}
	else{
		
	}
	if(dsu.findSz(0)!=n) return 0;
    vi U, V, A, B;
    for(auto edge : edges){
		U.pb(edge.fa), V.pb(edge.fb);
		A.pb(edge.x), B.pb(edge.y);
	}
	build(U,V,A,B); return 1;
}

• Subtask 1: 5 / 5
• Subtask 2: 10 / 10
• Subtask 3: 0 / 15
• Subtask 4: 0 / 20
• Subtask 5: 0 / 20
• Subtask 6: 0 / 30