제출 #527379

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
527379		jamielim	Pipes (CEOI15_pipes)	C++14	100 / 100	1398 ms	14200 KiB

pipes

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

#define fi first
#define se second
#define mp make_pair
#define pb emplace_back
#define ALL(x) x.begin(),x.end()
#define SZ(x) (int)x.size()
typedef long long ll;
typedef pair<int,int> ii;
typedef pair<ii,ii> i4;
const int MOD=1000000007;
const int INF=1012345678;
const ll LLINF=1012345678012345678LL;
const double PI=3.1415926536;
const double EPS=1e-14;

const int MAXN=100005;
int n,m;
int par[MAXN],par2[MAXN]; // par, depth
int root(int x){return par[x]=(par[x]==x?x:root(par[x]));}
int root2(int x){return par2[x]=(par2[x]==x?x:root2(par2[x]));}
vector<int> adj[MAXN]; // only stores at most 2*tree

int low[MAXN];
int ctr=0;
void dfs(int x){
	par2[x]=low[x]=ctr++;
	bool p=0;
	for(int i:adj[x]){
		if(i==par[x]&&!p){
			p=1;
			continue;
		}
		if(par2[i]==-1){
			par[i]=x;
			dfs(i);
			low[x]=min(low[x],low[i]);
			if(low[i]>par2[x])printf("%d %d\n",i+1,x+1);
		}else low[x]=min(low[x],par2[i]);
	}
}

int main(){
	scanf("%d%d",&n,&m);
	for(int i=0;i<n;i++)par[i]=par2[i]=i;
	int a,b;
	for(int i=0;i<m;i++){
		scanf("%d%d",&a,&b);a--;b--;
		//if a,b are in different trees, merge the two trees
		int ra=root(a),rb=root(b);
		if(ra!=rb){
			par[ra]=rb;
			adj[a].pb(b);
			adj[b].pb(a);
			continue;
		}
		//otherwise, take note that later we have to get rid of the entire cycle
		int r2a=root2(a),r2b=root2(b);
		if(r2a!=r2b){
			par2[r2a]=par2[r2b];
			adj[a].pb(b);
			adj[b].pb(a);
		}
	}
	memset(par,-1,sizeof(par));
	memset(par2,-1,sizeof(par2));
	memset(low,-1,sizeof(low));
	for(int i=0;i<n;i++)if(par2[i]==-1)dfs(i);
}

컴파일 시 표준 에러 (stderr) 메시지

pipes.cpp: In function 'int main()':
pipes.cpp:46:7: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   46 |  scanf("%d%d",&n,&m);
      |  ~~~~~^~~~~~~~~~~~~~
pipes.cpp:50:8: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   50 |   scanf("%d%d",&a,&b);a--;b--;
      |   ~~~~~^~~~~~~~~~~~~~

• Subtask 1: 10 / 10
• Subtask 2: 10 / 10
• Subtask 3: 10 / 10
• Subtask 4: 10 / 10
• Subtask 5: 10 / 10
• Subtask 6: 10 / 10
• Subtask 7: 10 / 10
• Subtask 8: 10 / 10
• Subtask 9: 10 / 10
• Subtask 10: 10 / 10