Implement Stack using Queues【225】

Datetime:2016-08-23 01:22:39          Topic: LeetCode           Share

Implement the following operations of a stack using queues.

  • push(x) -- Push element x onto stack.
  • pop() -- Removes the element on top of the stack.
  • top() -- Get the top element.
  • empty() -- Return whether the stack is empty.

Notes:

  • You must use  only  standard operations of a queue -- which means only  push to backpeek/pop from frontsize , and  is empty  operations are valid.
  • Depending on your language, queue may not be supported natively. You may simulate a queue by using a list or deque (double-ended queue), as long as you use only standard operations of a queue.
  • You may assume that all operations are valid (for example, no pop or top operations will be called on an empty stack).

Update (2015-06-11):

The class name of the  Java

function had been updated to 

MyStack

instead of Stack.

Credits:

Special thanks to  @jianchao.li.fighter for adding this problem and all test cases.





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