232.用栈实现队列
232.用栈实现队列
解题思路🤔
1、用栈来模拟队列的行为，需要使用两个栈，一个输入栈，一个输出栈。 2、一定要懂得复用代码！
代码⌨️
// 使用两个数组的栈方法（push, pop） 实现队列
/**
* Initialize your data structure here.
*/
var MyQueue = function() {
this.stackIn = [];
this.stackOut = [];
};
/**
* Push element x to the back of queue.
* @param {number} x
* @return {void}
*/
MyQueue.prototype.push = function(x) {
this.stackIn.push(x);
};
/**
* Removes the element from in front of queue and returns that element.
* @return {number}
*/
MyQueue.prototype.pop = function() {
const size = this.stackOut.length;
if(size) {
return this.stackOut.pop();
}
while(this.stackIn.length) {
this.stackOut.push(this.stackIn.pop());
}
return this.stackOut.pop();
};
/**
* Get the front element.
* @return {number}
*/
MyQueue.prototype.peek = function() {
const x = this.pop();
this.stackOut.push(x);
return x;
};
/**
* Returns whether the queue is empty.
* @return {boolean}
*/
MyQueue.prototype.empty = function() {
return !this.stackIn.length && !this.stackOut.length
};
225. 用队列实现栈
225. 用队列实现栈
解题思路🤔
1、用栈来模拟队列的行为，需要使用两个栈，一个输入栈，一个输出栈。 2、一定要懂得复用代码！
代码⌨️
// 使用两个队列实现
/**
* Initialize your data structure here.
*/
var MyStack = function() {
this.queue1 = [];
this.queue2 = [];
};
/**
* Push element x onto stack.
* @param {number} x
* @return {void}
*/
MyStack.prototype.push = function(x) {
this.queue1.push(x);
};
/**
* Removes the element on top of the stack and returns that element.
* @return {number}
*/
MyStack.prototype.pop = function() {
// 减少两个队列交换的次数， 只有当queue1为空时，交换两个队列
if(!this.queue1.length) {
[this.queue1, this.queue2] = [this.queue2, this.queue1];
}
while(this.queue1.length > 1) {
this.queue2.push(this.queue1.shift());
}
return this.queue1.shift();
};
/**
* Get the top element.
* @return {number}
*/
MyStack.prototype.top = function() {
const x = this.pop();
this.queue1.push(x);
return x;
};
/**
* Returns whether the stack is empty.
* @return {boolean}
*/
MyStack.prototype.empty = function() {
return !this.queue1.length && !this.queue2.length;
};
//使用一个队列
var MyStack = function() {
this.queue = [];
};
/**
* @param {number} x
* @return {void}
*/
MyStack.prototype.push = function(x) {
this.queue.push(x);
};
/**
* @return {number}
*/
MyStack.prototype.pop = function() {
let size = this.queue.length;
while(size-- > 1) {
this.queue.push(this.queue.shift());
}
return this.queue.shift();
};
/**
* @return {number}
*/
MyStack.prototype.top = function() {
const x = this.pop();
this.queue.push(x);
return x;
};
/**
* @return {boolean}
*/
MyStack.prototype.empty = function() {
return !this.queue.length;
};
