Submission #752026

#	Time	Username	Problem	Language	Result	Execution time	Memory
752026		minhcool	Parachute rings (IOI12_rings)	C++17	100 / 100	2008 ms	205328 KiB

rings

#include<bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
using namespace __gnu_pbds;
using namespace std;
 
#define ll long long
#define fi first
#define se second
#define pb push_back
#define mp make_pair
 
typedef pair<int, int> ii;
typedef pair<ii, int> iii;
typedef pair<ii, ii> iiii;
 
const int N = 1e6 + 5;
 
const int oo = 1e18 + 7, mod = 1e9 + 7;
 
mt19937 rng(1);
 
int n;
vector<int> Adj[N]; 
vector<ii> edges;
 
int deg[N], mx_deg;
 
int cur_ans = 0;
 
int szz[N], rtt[N];
 
void Init(int N_) {
	n = N_;
	for(int i = 1; i <= n; i++){
		szz[i] = 1, rtt[i] = i;	
	}
	cur_ans = n;
}
 
int cnt;
vector<int> candidates;
 
int deg2[N][8], mxdeg[8];
 
bool out[N];
 
int sz[N][8], rt[N][8];
 
void init(int ind){
	for(int i = 1; i <= n; i++){
		sz[i][ind] = 1, rt[i][ind] = i;
		deg2[i][ind] = 0;
	}
	mxdeg[ind] = 0;
	out[ind] = 0;
}
 
int root(int x, int ind){
	return (x == rt[x][ind] ? x : rt[x][ind] = root(rt[x][ind], ind));
}
 
bool merge(int x, int y, int ind){
	x = root(x, ind), y = root(y, ind);
	if(x == y) return 0;
	if(sz[x][ind] < sz[y][ind]) swap(x, y);
	sz[x][ind] += sz[y][ind];
	rt[y][ind] = x;
	return 1;
}
 
void add_edge(int x, int y, int ind){
	if(x == candidates[ind - 1] || y == candidates[ind - 1]) return;
	deg2[x][ind]++, deg2[y][ind]++;
	mxdeg[ind] = max(mxdeg[ind], deg2[x][ind]);
	mxdeg[ind] = max(mxdeg[ind], deg2[y][ind]);
	out[ind] |= (!merge(x, y, ind));
	out[ind] |= (mxdeg[ind] >= 3);
}
 
 
int roott(int x){
	return (x == rtt[x] ? x : rtt[x] = roott(rtt[x]));
}
 
bool mergee(int x, int y){
	x = roott(x), y = roott(y);
	if(x == y) return 0;
	if(szz[x] < szz[y]) swap(x, y);
	szz[x] += szz[y];
	rtt[y] = x;
	return 1;
}
 
int tol_cyc = 0;
 
int d[N];
 
vector<int> Ad[N];
 
void dfs(int u, int p){
	for(auto v : Adj[u]){
		if(v == p) continue;
		d[v] = d[u] + 1;
		dfs(v, u);
	}
}
 
set<int> se;
 
void Link(int A, int B) {
	A++, B++;
	//Adj[A].pb(B);
	//Adj[B].pb(A);
	Ad[A].pb(B);
	Ad[B].pb(A);
    //if(deg[A] == 3) se.erase(A);
    //if(deg[B] == 3) se.erase(B);
	edges.pb({A, B});
	int old = mx_deg;
	//se.erase({deg[A], A});
	//se.erase({deg[B], B});
	deg[A]++;
	deg[B]++;
    if(deg[A] == 3 && se.size() <= 4) se.insert(A);
    if(deg[B] == 3 && se.size() <= 4) se.insert(B);
	//se.insert({deg[A], A});
	//se.insert({deg[B], B});
	mx_deg = max(mx_deg, deg[A]);
	mx_deg = max(mx_deg, deg[B]);
	if(mx_deg <= 2){
        if(tol_cyc >= 2) return;
		int lst = tol_cyc;
		tol_cyc += (!mergee(A, B));
		if(tol_cyc == 2) cur_ans = 0;
		else if(!tol_cyc) cur_ans = n;
		else{
			if(lst == 1) return;
			for(int i = 0; (i + 1) < edges.size(); i++){
				Adj[edges[i].fi].pb(edges[i].se);
				Adj[edges[i].se].pb(edges[i].fi);
			}
			dfs(A, A);
			cur_ans = d[B] + 1;
		}
	}
	else if(mx_deg == 3){
	//	cout << "OK " << cnt << "\n";
		int counter = se.size();
		if(counter > 4){
			cur_ans = 0;
			return;
		}
		int lst_cnt = cnt;
		if(deg[A] >= 3){
			bool ck = 1;
			for(auto it : candidates) ck &= (it != A);
			if(ck){
				cnt++;
				init(cnt);
				candidates.pb(A);
				for(auto it : edges) add_edge(it.fi, it.se, cnt);
			}
			for(auto it : Ad[A]){		
				bool ck = 1;
				for(auto it2 : candidates) ck &= (it != it2);
				int cn = 0;
				for(auto it2 : Ad[it]) cn += (deg[it2] >= 3);
				ck &= (cn == counter); 
				if(ck){
					cnt++;
					init(cnt);
					candidates.pb(it);
					for(auto it2 : edges) add_edge(it2.fi, it2.se, cnt);
				}
			}
		}
		if(deg[B] >= 3){
			bool ck = 1;
			for(auto it : candidates) ck &= (it != B);
			if(ck){
				cnt++;
				init(cnt);
				candidates.pb(B);
				for(auto it : edges) add_edge(it.fi, it.se, cnt);
			}
			for(auto it : Ad[B]){		
				bool ck = 1;
				for(auto it2 : candidates) ck &= (it != it2);
				int cn = 0;
				for(auto it2 : Ad[it]) cn += (deg[it2] >= 3);
				ck &= (cn == counter); 
				if(ck){
					cnt++;
					init(cnt);
					candidates.pb(it);
					for(auto it2 : edges) add_edge(it2.fi, it2.se, cnt);
				}
			}
		}
	//	exit(0);
		for(int i = 1; i <= lst_cnt; i++) add_edge(A, B, i);
		cur_ans = 0;
		for(int i = 1; i <= cnt; i++) cur_ans += (!out[i]);
	}
	else{
		//cout << "OK\n";
		if(old < 4){
			candidates.clear();
			cnt = 0;
		}
        else{
          if(cnt >= 2) return;
		}
		if(deg[A] >= 4){
			bool ck = 1;
			for(auto it : candidates) ck &= (it != A);
			if(ck){
				cnt++;
				candidates.pb(A);
			}
		}
		if(deg[B] >= 4){
			bool ck = 1;
			for(auto it : candidates) ck &= (it != B);
			if(ck){
				cnt++;
				candidates.pb(B);
			}
		}
	//	cout << cnt << "\n";
		if(cnt >= 2){
			cur_ans = 0;
			return;
		}
		if(old < 4){// build new graph
			init(1);
			assert(cnt == 1);
			for(auto it : edges) add_edge(it.fi, it.se, 1);
		}
		else{
			add_edge(A, B, 1);
		}
		cur_ans = (!out[1]);
	}
}
 
int CountCritical() {
	return cur_ans;
}
 
/*
void process(){
	int n;
	cin >> n;
	Init(n);
	int m;
	cin >> m;
	for(int i = 1; i <= m; i++){
		int x, y;
		cin >> x >> y;
		Link(x, y);
		cout << CountCritical() << "\n";
	}
}
 
signed main(){
	process();
}*/

Compilation message (stderr)

rings.cpp:18:21: warning: overflow in conversion from 'double' to 'int' changes value from '1.0e+18' to '2147483647' [-Woverflow]
   18 | const int oo = 1e18 + 7, mod = 1e9 + 7;
      |                ~~~~~^~~
rings.cpp: In function 'void Link(int, int)':
rings.cpp:138:27: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  138 |    for(int i = 0; (i + 1) < edges.size(); i++){
      |                   ~~~~~~~~^~~~~~~~~~~~~~

• Subtask 1: 20 / 20
• Subtask 2: 17 / 17
• Subtask 3: 18 / 18
• Subtask 4: 14 / 14
• Subtask 5: 31 / 31