Submission #350960

#	Time	Username	Problem	Language	Result	Execution time	Memory
350960		tengiz05	Parachute rings (IOI12_rings)	C++17	55 / 100	4056 ms	68832 KiB

rings

#ifndef EVAL
#include "grader.cpp"
#endif
#include <bits/stdc++.h>
using namespace std;
#define pb push_back
const int Ni = 1e6+5;
vector<int> edges[Ni];
int n, ans;


// start of DSU
vector<int> p, sz, cyclic;
int par(int u){
	if(p[u] == u)return u;
	return p[u] = par(p[u]);
}
bool IsSame(int u, int v){
	return par(u) == par(v);
}
void merge(int u,int v){
	u=par(u);v=par(v);
	if(u == v)return;
	p[v] = u;
	sz[u] += sz[v];
	cyclic[u] |= cyclic[v];
	return;
}
int size_of_node(int u){
	return sz[par(u)];
}// end of DSU


int have_this_number_of_edges[5];
void Init(int N_) {
	n = N_;
	ans = n;
	p.assign(n,0);
	sz.assign(n,1);
	cyclic.assign(n,0);
	for(int i=0;i<n;i++)p[i] = i;
	have_this_number_of_edges[0] = n;
}
int number_of_cycles;
void del(int u){
	have_this_number_of_edges[min(4,(int)edges[u].size())]--;
}void add(int u){
	have_this_number_of_edges[min(4,(int)edges[u].size())]++;	
}
void Link(int u, int v){
	del(u);del(v);
	edges[u].pb(v);
	edges[v].pb(u);
	add(u);add(v);
	if(IsSame(u, v)){
		number_of_cycles++;
		cyclic[par(u)] = 1;
	}else {
		merge(u,v);
	}return;
}

int please_dont_go_there;
bool is_it_normal;
bool used[Ni];

void dfs(int u, int p){
	used[u] = true;
	int cnt = 0;
	for(auto v : edges[u]){
		if(v != please_dont_go_there)cnt++;
		if(v == p || v == please_dont_go_there)continue;
		if(used[v])is_it_normal = false;
		else dfs(v,u);
	}if(cnt>2)is_it_normal = false;
}

bool CheckItPlease(int to_delete){
	please_dont_go_there = to_delete;
	for(int j=0;j<n;j++)used[j] = false;
	used[please_dont_go_there] = true;
	is_it_normal = true;
	for(int j=0;j<n;j++){
		if(!used[j])dfs(j,j);
	}return is_it_normal;
}

int CountCritical(){
	if(have_this_number_of_edges[4] > 1)return 0;
	if(!number_of_cycles && have_this_number_of_edges[3]+have_this_number_of_edges[4]==0)return n;
	ans = 0;
	if(have_this_number_of_edges[4] == 1){
		int we_need_it;
		for(int i=0;i<n;i++){
			if(edges[i].size() >= 4){
				we_need_it = i;break;
			}
		}
		ans += CheckItPlease(we_need_it);
	}else if(have_this_number_of_edges[3] > 0){
		int we_need_it=-1;
		for(int i=0;i<n;i++){
			if(edges[i].size() == 3){
				we_need_it = i;break;
			}
		}assert(~we_need_it);
		ans += CheckItPlease(we_need_it);
		for(auto v : edges[we_need_it])ans += CheckItPlease(v);	
	}else if(have_this_number_of_edges[2] > 0){
		if(number_of_cycles > 1)return 0;
		for(int i=0;i<n;i++){
			if(cyclic[par(i)])return size_of_node(i);
		}assert(false);
	}else assert(false);
	return ans;
}

Compilation message (stderr)

rings.cpp: In function 'int CountCritical()':
rings.cpp:99:23: warning: 'we_need_it' may be used uninitialized in this function [-Wmaybe-uninitialized]
   99 |   ans += CheckItPlease(we_need_it);
      |          ~~~~~~~~~~~~~^~~~~~~~~~~~

• Subtask 1: 20 / 20
• Subtask 2: 17 / 17
• Subtask 3: 18 / 18
• Subtask 4: 0 / 14
• Subtask 5: 0 / 31