算法题:
- 链接:https://leetcode-cn.com/problems/implement-queue-using-stacks/
- 描述:
- 请你仅使用两个栈实现先入先出队列。队列应当支持一般队列支持的所有操作(push、pop、peek、empty):
- 实现 MyQueue 类:
- void push(int x) 将元素 x 推到队列的末尾
- int pop() 从队列的开头移除并返回元素
- int peek() 返回队列开头的元素
- boolean empty() 如果队列为空,返回 true ;否则,返回 false
- 说明:
- 你 只能 使用标准的栈操作 —— 也就是只有 push to top, peek/pop from top, size, 和 is empty 操作是合法的。
你所使用的语言也许不支持栈。你可以使用 list 或者 deque(双端队列)来模拟一个栈,只要是标准的栈操作即可。
- 示例 ```javascript 输入: [“MyQueue”, “push”, “push”, “peek”, “pop”, “empty”] [[], [1], [2], [], [], []] 输出: [null, null, null, 1, 1, false]
解释: MyQueue myQueue = new MyQueue(); myQueue.push(1); // queue is: [1] myQueue.push(2); // queue is: [1, 2] (leftmost is front of the queue) myQueue.peek(); // return 1 myQueue.pop(); // return 1, queue is [2] myQueue.empty(); // return false
- 答案
```javascript
var MyQueue = function () {
this.inStack = []
this.outStack = []
};
/**
* @param {number} x
* @return {void}
*/
MyQueue.prototype.push = function (x) {
this.inStack[this.inStack.length] = x
};
/**
* @return {number}
*/
MyQueue.prototype.pop = function () {
if (this.outStack.length === 0) {
for (let i = this.inStack.length - 1; i >= 0; i--) {
this.outStack[this.inStack.length - 1 - i] = this.inStack[i]
}
this.inStack = []
console.log('outStack',this.outStack)
}
let result = this.outStack[this.outStack.length-1]
this.outStack = this.outStack.slice(0,this.outStack.length-1)
return result
};
/**
* @return {number}
*/
MyQueue.prototype.peek = function () {
if (this.outStack.length === 0) {
for (let i = this.inStack.length - 1; i >=0; i--) {
this.outStack[this.inStack.length - 1 - i] = this.inStack[i]
}
this.inStack = []
}
return this.outStack[this.outStack.length-1]
};
/**
* @return {boolean}
*/
MyQueue.prototype.empty = function () {
return this.inStack.length === 0 && this.outStack.length === 0
};
手写题:
- 链接:https://bigfrontend.dev/zh/problem/the-angle-between-hour-hand-and-minute-hand-of-a-clock
- 描述:请计算出时钟的时针和分针的角度(两个角度的较小者,四舍五入)。时间以HH:mm的格式传入。
- 示例 ```javascript angle(‘12:00’) // 0
angle(‘23:30’) // 165
- 解答
```javascript
function angle(time) {
// your code here
let [hour,min] = time.split(':')
let hourAngle = Number(hour)%12*(360/12)+(min/60)*(360/12)
let minAngle = Number(min)*(360/60)
let abs = Math.abs(hourAngle-minAngle)
return Math.round(abs>180?360-abs:abs)
}
- 问题:
- 没有考虑时针的偏移
- 没有考虑最小角度