Submission #310728

#	Time	Username	Problem	Language	Result	Execution time	Memory
310728		rqi	Roller Coaster Railroad (IOI16_railroad)	C++14	100 / 100	617 ms	40244 KiB

railroad

#include "railroad.h"
#include <bits/stdc++.h>
 
using namespace std;
 
typedef long long ll;
typedef vector<int> vi;
typedef pair<int, int> pi;
typedef vector<pi> vpi;
 
#define sz(x) (int)(x).size()
#define all(x) begin(x), end(x)
#define mp make_pair
#define pb push_back
#define f first
#define s second

struct DSU{
	vi e;
	void init(int n){
		e = vi(n, -1);
	}
	int get(int a){
		if(e[a] < 0) return a;
		e[a] = get(e[a]);
		return e[a];
	}
	bool unite(int a, int b){
		a = get(a);
		b = get(b);
		if(a == b) return 0;
		if(-e[a] < -e[b]) swap(a, b);
		e[a]+=e[b];
		e[b] = a;
		return 1;
	}
};
 
ll plan_roller_coaster(vi s, vi t) {
	s.pb(1000000000);
	t.pb(0);
	int n = sz(s);

	vpi v;
	for(int i = 0; i < n; i++){
		v.pb(mp(s[i], -1));
		v.pb(mp(t[i], 1));
	}
	sort(all(v));
	map<int, int> rv;

	for(int i = 0; i < 2*n; i++){
		//cout << i << " " << v[i].f << "\n";
		rv[v[i].f] = i;
	}

	DSU dsu;
	dsu.init(2*n);

	for(int i = 0; i < n; i++){
		dsu.unite(rv[s[i]], rv[t[i]]);
	}

	ll ans = 0;
	for(int i = 0; i < 2*n; i++){
		if(i-1 >= 0) v[i].s+=v[i-1].s;
		if(i+1 < 2*n){
			if(v[i].s < 0){
				dsu.unite(i, i+1);
				ans+=ll(v[i+1].f-v[i].f)*ll(-v[i].s);
				//cout << "<: " << i << " " << i+1 << "\n";
			}
			else if(v[i].s > 0){
				dsu.unite(i, i+1);
				//cout << ">: " << i << " " << i+1 << "\n";
			}
		}
	}

	vector<pair<int, pi>> eds;

	for(int i = 0; i+1 < 2*n; i++){
		eds.pb(mp(v[i+1].f-v[i].f, mp(i, i+1)));
	}

	sort(all(eds));

	for(auto u: eds){
		if(dsu.unite(u.s.f, u.s.s)){
			ans+=u.f;
		}
	}
	
	return ans;
}

• Subtask 1: 11 / 11
• Subtask 2: 23 / 23
• Subtask 3: 30 / 30
• Subtask 4: 36 / 36