Submission #868885

#	Time	Username	Problem	Language	Result	Execution time	Memory
868885		pcc	Matching (COCI20_matching)	C++14	0 / 110	5 ms	22872 KiB

matching

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

#define ll long long
#define pll pair<ll,ll>
#define pii pair<int,int>
#define fs first
#define sc second
#define tlll tuple<ll,ll,ll>

const int mxn = 2e5+10;
const int inf = 1e9;

struct Edge{
	int flow,cap,to;
	Edge(int a,int b){
		to = a,cap = b;
		flow = 0;
	}
	Edge(){}
};

bitset<mxn> vis;
vector<Edge> edges;
vector<int> paths[mxn],g[mxn];
vector<pii> dx[mxn],dy[mxn];
int level[mxn],col[mxn],ptr[mxn];
pii arr[mxn];
int n;
queue<int> q;

void dfs1(int now,int c){
	col[now] = c;
	for(auto nxt:g[now]){
		if(!col[nxt])dfs1(nxt,-c);
	}
	return;
}

void addedge(int s,int e,int v){
	paths[s].push_back(edges.size());
	edges.push_back(Edge(e,v));
	paths[e].push_back(edges.size());
	edges.push_back(Edge(s,0));
	return;
}
bool bfs(){
	memset(level,-1,sizeof(level));
	queue<int> q;
	level[0] = 0;
	q.push(0);
	while(!q.empty()){
		auto now = q.front();
		q.pop();
		for(auto &eid:paths[now]){
			if(!(edges[eid].cap-edges[eid].flow))continue;
			int nxt = edges[eid].to;
			if(level[nxt] == -1){
				level[nxt] = level[now]+1;
				q.push(nxt);
			}
		}
	}
	return level[n+1]!= -1;
}

int dfs(int now,int f){
	if(now == n+1)return f;
	for(int &i = ptr[now];i<paths[now].size();i++){
		int eid = paths[now][i];
		int nxt = edges[eid].to;
		if(level[nxt] != level[now]+1||edges[eid].cap-edges[eid].flow == 0)continue;
		int re = dfs(nxt,min(f,edges[eid].cap-edges[eid].flow));
		if(!re)continue;
		edges[eid].flow += re;
		edges[eid^1].flow -= re;
		return re;
	}
	return 0;
}

int main(){
	ios::sync_with_stdio(0);cin.tie(0);cout.tie(0);
	cin>>n;
	for(int i = 1;i<=n;i++){
		cin>>arr[i].fs>>arr[i].sc;
		dx[arr[i].fs].push_back({arr[i].sc,i});
		dy[arr[i].sc].push_back({arr[i].fs,i});
	}
	for(auto &i:dx)sort(i.begin(),i.end());
	for(auto &i:dy)sort(i.begin(),i.end());
	for(int i = 1;i<=n;i++){
		auto it = lower_bound(dx[arr[i].fs].begin(),dx[arr[i].fs].end(),make_pair(arr[i].sc,-inf));
		if(it != dx[arr[i].fs].begin()){
			it--;
			g[it->sc].push_back(i);
			g[i].push_back(it->sc);
		}
		it = upper_bound(dx[arr[i].fs].begin(),dx[arr[i].fs].end(),make_pair(arr[i].sc,inf));
		if(it != dx[arr[i].fs].end()){
			g[it->sc].push_back(i);
			g[i].push_back(it->sc);
		}
		it = lower_bound(dy[arr[i].sc].begin(),dy[arr[i].sc].end(),make_pair(arr[i].fs,-inf));
		if(it != dy[arr[i].sc].begin()){
			it--;
			g[it->sc].push_back(i);
			g[i].push_back(it->sc);
		}
		it = upper_bound(dy[arr[i].sc].begin(),dy[arr[i].sc].end(),make_pair(arr[i].fs,inf));
		if(it != dy[arr[i].sc].end()){
			g[it->sc].push_back(i);
			g[i].push_back(it->sc);
		}
	}
	for(int i = 1;i<=n;i++){
		if(!col[i])dfs1(i,1);
	}
	for(int i = 1;i<=n;i++){
		sort(g[i].begin(),g[i].end());
		g[i].resize(unique(g[i].begin(),g[i].end())-g[i].begin());
	}
	/*
	for(int i = 1;i<=n;i++){
		for(auto &j:g[i])cout<<i<<' '<<j<<' '<<col[i]*col[j]<<' ';cout<<endl;
	}for(int i = 1;i<=n;i++)cout<<col[i]<<' ';cout<<endl;

   */
	for(int i = 1;i<=n;i++){
		if(col[i] == -1){
			addedge(i,n+1,1);
			continue;
		}
		addedge(0,i,1);
		for(auto nxt:g[i])addedge(i,nxt,1);
	}
	/*
	for(int i = 1;i<=n;i++){
		for(auto eid:paths[i]){
			cout<<i<<','<<edges[eid].to<<' '<<edges[eid].cap<<','<<edges[eid].flow<<endl;
		}
	}

   */
	int f = 0;
	while(bfs()){
		memset(ptr,0,sizeof(ptr));
		int re = 0;
		while((re = dfs(0,inf)))f += re;
	}
	//cout<<f<<endl;
	if(f != n/2){
		cout<<"NE\n";
		return 0;
	}
	vector<pii> ans;
	for(int i = 1;i<=n;i++){
		if(col[i] == -1)continue;
		for(auto &eid:paths[i]){
			if(edges[eid].cap-edges[eid].flow)continue;
			int nxt = edges[eid].to;
			if(nxt)ans.push_back({i,nxt});
		}
	}
	cout<<"DA\n";
	for(auto &i:ans)cout<<i.fs<<' '<<i.sc<<'\n';
	return 0;
}

Compilation message (stderr)

matching.cpp: In function 'int dfs(int, int)':
matching.cpp:69:25: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   69 |  for(int &i = ptr[now];i<paths[now].size();i++){
      |                        ~^~~~~~~~~~~~~~~~~~

• Subtask 1: 0 / 5
• Subtask 2: 0 / 6
• Subtask 3: 0 / 7
• Subtask 4: 0 / 40
• Subtask 5: 0 / 52