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Implement queue using stacks

(3 posts)

1. 

   Shekhu
   guest
   Posted 2 years ago #
   
   

   How will implement queue using 2 stacks such that enqueue and dequeue operations are efficient

2. 

   geek4u
   guest
   Posted 2 years ago #
   
   

   Here is a pseudo code using two stacks. Let two stacks be S1 and S2 and queue is Q.

   For enqueue operation, push in buffer stack S1.
   For dequeue operation, if S2 is not empty then pop and return top element of S2, otherwise push everything from S1 to S2 and then pop and return the top element of S2

   void enQueue(Q,  x)
   {
       push (S1,  x);
   }
   
   void deQueue(Q)
   {
      if (isStackEmpty(52))
      {
        if (isStackEmpty(S1))
        {
             print(”Q is empty”);
             return;
        }
        else
        {
            while (!(isStackEmpty(S1)))
            {
                 x = pop(S1);
                push(S2,  x)
            }
        }     
   
        x = pop (S2);
        return x;
   }
   

3. 

   GeeksforGeeks
   Key Master
   Posted 2 years ago #
   
   

   This has been published. Please see http://geeksforgeeks.org/?p=5009

   Thanks all for your contribution.

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