刷题笔记day10-栈和队列01

232.用栈实现队列

思路就是用一个切片，每次追加在后面，但是取值从最前面取值。

// 用两个栈来实现队列的先进先出的效果
// peek、push、pop、empty

type MyQueue struct {
    push []int
    pop []int
}


func Constructor() MyQueue {
    return MyQueue {
        push: []int{},
        pop: []int{},
    }
}

func (this *MyQueue) pushToPop() {
    // pop 必须是为空的，才可以进行移动
    if len(this.pop) == 0 {
        push_length := len(this.push) - 1
        for push_length >= 0 {
            this.pop = append(this.pop, this.push[push_length])
            this.push = this.push[:push_length]
            push_length--
        }
    }
}


func (this *MyQueue) Push(x int)  {
    // 
    this.push = append(this.push, x)
    // 移动
    this.pushToPop()
}


func (this *MyQueue) Pop() int {
    // 先移动
    this.pushToPop()
    // if len(this.pop) <= 0 {
    //     return 
    // }
    top := this.pop[len(this.pop) - 1]
    this.pop = this.pop[:len(this.pop) - 1]
    return top
}


func (this *MyQueue) Peek() int {
    // 先移动
    this.pushToPop()
    return this.pop[len(this.pop) - 1]
}


func (this *MyQueue) Empty() bool {
    this.pushToPop()
    return len(this.pop) <= 0
}


/**
 * Your MyQueue object will be instantiated and called as such:
 * obj := Constructor();
 * obj.Push(x);
 * param_2 := obj.Pop();
 * param_3 := obj.Peek();
 * param_4 := obj.Empty();
 */

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225. 用队列实现栈