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95 lines
2.0 KiB
Markdown
95 lines
2.0 KiB
Markdown
# [225. Implement Stack using Queues](https://leetcode.com/problems/implement-stack-using-queues/)
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## 题目
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Implement the following operations of a stack using queues.
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- push(x) -- Push element x onto stack.
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- pop() -- Removes the element on top of the stack.
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- top() -- Get the top element.
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- empty() -- Return whether the stack is empty.
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**Example**:
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```
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MyStack stack = new MyStack();
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stack.push(1);
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stack.push(2);
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stack.top(); // returns 2
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stack.pop(); // returns 2
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stack.empty(); // returns false
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```
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**Note**:
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- 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.
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- 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.
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- You may assume that all operations are valid (for example, no pop or top operations will be called on an empty stack).
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## 题目大意
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题目要求用队列实现一个栈的基本操作：push(x)、pop()、top()、empty()。
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## 解题思路
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按照题目要求实现即可。
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## 代码
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```go
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package leetcode
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type MyStack struct {
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enque []int
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deque []int
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}
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/** Initialize your data structure here. */
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func Constructor225() MyStack {
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return MyStack{[]int{}, []int{}}
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}
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/** Push element x onto stack. */
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func (this *MyStack) Push(x int) {
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this.enque = append(this.enque, x)
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}
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/** Removes the element on top of the stack and returns that element. */
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func (this *MyStack) Pop() int {
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length := len(this.enque)
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for i := 0; i < length-1; i++ {
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this.deque = append(this.deque, this.enque[0])
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this.enque = this.enque[1:]
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}
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topEle := this.enque[0]
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this.enque = this.deque
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this.deque = nil
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return topEle
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}
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/** Get the top element. */
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func (this *MyStack) Top() int {
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topEle := this.Pop()
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this.enque = append(this.enque, topEle)
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return topEle
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}
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/** Returns whether the stack is empty. */
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func (this *MyStack) Empty() bool {
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if len(this.enque) == 0 {
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return true
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}
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return false
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}
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``` |