Leetcode 232 Implement Queue using Stacks

Implement the following operations of a queue using stacks.

• Push (x)--push element x to the back of the queue.
• Pop ()--Removes the element from in front of the queue.
• Peek ()--Get the front element.
• Empty ()--Return whether the queue is empty.

  Notes:

  • You must use only standard operations of a stack--which means only push to top , peek/pop from top , size , and is empty operations AR E valid.
  • Depending on your language, stack may is not supported natively. You could simulate a stack by using a list or deque (double-ended queue), as long as if you have standard operations of a s Tack.
  • You may assume this all operations is valid (for example, no pop or peek operations would be called on an empty queue).

Ideas:

Using two stacks, each time the operation of the queue, the elements of a stack are ejected, and then in the stack of elements pressed into the queue element, then the stack of all the elements popped, press back to the first stack.

Solution:

1 ImportJava.util.Stack;2 3  Public classMyqueue4 {5     PrivateStack<integer>Inputstack;6     PrivateStack<integer>Outputstack;7 8      Publicmyqueue ()9     {TenInputstack =NewStack<>(); OneOutputstack =NewStack<>(); A     } -  -      Public voidPushintx) the     { -          while(!outputstack.isempty ()) - Inputstack.push (Outputstack.pop ()); - Inputstack.push (x); +          while(!inputstack.isempty ()) - Outputstack.push (Inputstack.pop ()); +     } A  at      Public voidpop () - {Outputstack.pop ();} -  -      Public intPeek () -{returnOutputstack.peek ();} -  in      Public Booleanempty () -{returnoutputstack.isempty ();} to}

Leetcode 232 Implement Queue using Stacks