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  1. #include <bits/stdc++.h>
  2.  
  3. using namespace std;
  4.  
  5. int n,e,u,v;
  6.  
  7. set < int > myset[100005];
  8.  
  9. stack < int > temp_path;
  10.  
  11. vector < int > vec(100005);
  12.  
  13. bool chk_euler()
  14. {
  15. 	for(int i=1;i<=n;i++)
  16. 	{
  17. 		if((myset[i].size()&1)) return 0;
  18. 	}
  19.  
  20. 	return 1;
  21. }
  22.  
  23. bool euler_dfs(int ref)
  24. {	
  25. 	temp_path.push(ref);
  26.  
  27. 	set < int >::iterator it;
  28.  
  29. 	int k=e;
  30.  
  31. 	while(!temp_path.empty())
  32. 	{
  33. 		int ver=temp_path.top();
  34.  
  35. 		if(myset[ver].size()!=0)
  36. 		{
  37. 			it=myset[ver].begin();
  38.  
  39. 			myset[ver].erase(*it);
  40.  
  41. 			myset[*it].erase(ver);
  42.  
  43. 			temp_path.push(*it);	
  44. 		}
  45.  
  46. 		else
  47. 		{
  48. 			vec[k]=ver; k--;
  49.  
  50. 			temp_path.pop();
  51. 		}	
  52. 	}
  53.  
  54. 	cout<<"YES\n";
  55.  
  56. 	for(int i=0;i<e;i++)
  57. 	{
  58. 		cout<<vec[i]<<" "<<vec[i+1]<<"\n";
  59. 	}
  60. }
  61.  
  62. int main()
  63. {
  64. 	ios_base::sync_with_stdio(false);
  65.  
  66. 	cin.tie(NULL);
  67.  
  68. 	cin>>n>>e;
  69.  
  70. 	int ref;
  71.  
  72. 	for(int i=0;i<e;i++)
  73. 	{
  74. 		cin>>u>>v;
  75.  
  76. 		if(i==0) ref=u;
  77.  
  78. 		myset[u].insert(v);
  79.  
  80. 		myset[v].insert(u);
  81. 	}
  82.  
  83. 	if(chk_euler())
  84. 	{
  85. 		euler_dfs(ref);
  86. 	}
  87.  
  88. 	else cout<<"NO\n";
  89.  
  90. 	return 0;
  91. }
Success #stdin #stdout 0s 19936KB
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YES
https://ideone.com/pqofJS
language:
C++ (gcc 8.3)
created:
6 years ago
visibility:
public

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