剑指 Offer 09. 用两个栈实现队列

题目描述

用两个栈实现一个队列。队列的声明如下，请实现它的两个函数 appendTail 和 deleteHead ，分别完成在队列尾部插入整数和在队列头部删除整数的功能。(若队列中没有元素，deleteHead 操作返回 -1 )

示例 1：

输入： [“CQueue”,“appendTail”,“deleteHead”,“deleteHead”,“deleteHead”] [[],[3],[],[],[]]
输出：[null,null,3,-1,-1]

示例 2：

输入： [“CQueue”,“deleteHead”,“appendTail”,“appendTail”,“deleteHead”,“deleteHead”] [[],[],[5],[2],[],[]]
输出：[null,-1,null,null,5,2]

提示：

1 <= values <= 10000
最多会对 appendTail、deleteHead 进行 10000 次调用

解法一：模拟

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type CQueue struct {
    inStack []int
    outStack []int
}


func Constructor() CQueue {
    return CQueue{}
}


func (this *CQueue) AppendTail(value int)  {
    this.inStack = append(this.inStack, value)
}


func (this *CQueue) DeleteHead() int {
    inStack, outStack := this.inStack, this.outStack
    if len(outStack) == 0 {
        if len(inStack) == 0 {
            return -1
        }
        for len(inStack) > 0 {
            outStack = append(outStack, inStack[len(inStack)-1])
            inStack = inStack[:len(inStack)-1]
        }
    }
    res := outStack[len(outStack)-1]
    outStack = outStack[:len(outStack)-1]
    this.inStack = inStack
    this.outStack = outStack
    return res
}

/**
 * Your CQueue object will be instantiated and called as such:
 * obj := Constructor();
 * obj.AppendTail(value);
 * param_2 := obj.DeleteHead();
 */