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  1. #include <iostream>
  2. #include <queue>
  3.  
  4. using namespace std;
  5.  
  6. class queue_stack
  7. {
  8. public:
  9.   void push(int n);
  10.   void pop();
  11.   int peek();
  12.   bool empty();
  13. private:
  14.   queue<int> q1, q2;
  15. };
  16.  
  17. void queue_stack::push(int n)
  18. {
  19.   q2.push(n);
  20.   while (!q1.empty())
  21.   {
  22.   	q2.push(q1.front());
  23.   	q1.pop();
  24.   }
  25.   q1.swap(q2);
  26. }
  27.  
  28. void queue_stack::pop()
  29. {
  30.   q1.pop();
  31. }
  32.  
  33. int queue_stack::peek()
  34. {
  35. 	return q1.front();
  36. }
  37.  
  38. bool queue_stack::empty()
  39. {
  40. 	return q1.empty();
  41. }
  42.  
  43. void assert(int expected, int actual)
  44. {
  45. 	if (expected != actual)
  46. 	{
  47. 		cout << "Expected " << expected << " got " << actual << endl;
  48. 	}
  49. }
  50.  
  51. int main()
  52. {
  53.     queue_stack s;
  54.     s.push(1);
  55.     assert(1, s.peek());
  56.     s.push(2);
  57.     assert(2, s.peek());
  58.     s.push(3);
  59.     assert(3, s.peek());
  60.     s.pop();
  61.     assert(2, s.peek());
  62.     for (int i = 3; i <= 50; i++)
  63.     {
  64.     	s.push(i);
  65.     	assert(i, s.peek());
  66.     }
  67.  
  68.     int i;
  69.     for (i = 50; !s.empty(); i--)
  70.     {
  71.     	assert(i, s.peek());
  72.     	s.pop();
  73.     }
  74.     assert(0, i);
  75. 	return 0;
  76. }
Success #stdin #stdout 0s 3428KB
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https://ideone.com/VFzsK2
language:
C++14 (gcc 8.3)
created:
9 years ago
visibility:
public

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