problem0225

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225. Implement Stack using Queues

题目

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:

1. You must use only standard operations of a queue -- which means only push to back, peek/pop from front, size, and is empty operations are valid.
2. 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.
3. You may assume that all operations are valid (for example, no pop or top operations will be called on an empty stack).

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

解题思路

见程序注释

Documentation

Index

• type MyStack
  • func Constructor() MyStack
  • func (ms *MyStack) Empty() bool
  • func (ms *MyStack) Pop() int
  • func (ms *MyStack) Push(x int)
  • func (ms *MyStack) Top() int
• type Queue
  • func NewQueue() *Queue
  • func (q *Queue) IsEmpty() bool
  • func (q *Queue) Len() int
  • func (q *Queue) Pop() int
  • func (q *Queue) Push(n int)

Types

type MyStack

type MyStack struct {
	// contains filtered or unexported fields
}

MyStack 是用 Queue 实现的 栈

func Constructor

func Constructor() MyStack

Constructor Initialize your data structure here.

func (*MyStack) Empty

func (ms *MyStack) Empty() bool

Empty Returns whether the stack is empty.

func (*MyStack) Pop

func (ms *MyStack) Pop() int

Pop Removes the element on top of the stack and returns that element.

func (*MyStack) Push

func (ms *MyStack) Push(x int)

Push Push element x onto stack.

func (*MyStack) Top

func (ms *MyStack) Top() int

Top Get the top element.

type Queue

type Queue struct {
	// contains filtered or unexported fields
}

Queue 是用于存放 int 的队列

func NewQueue

func NewQueue() *Queue

NewQueue 返回 *kit.Queue

func (*Queue) IsEmpty

func (q *Queue) IsEmpty() bool

IsEmpty 反馈 q 是否为空

func (*Queue) Len

func (q *Queue) Len() int

Len 返回 q 的长度

func (*Queue) Pop

func (q *Queue) Pop() int

Pop 从 q 中取出最先进入队列的值

func (*Queue) Push

func (q *Queue) Push(n int)

Push 把 n 放入队列