剑指 Offer 09. 用两个栈实现队列
问题描述：
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"]
[[],[3],[],[]]
输出：[null,null,3,-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
import scala.collection.mutable.Stack
class CQueue() {
val fStack = Stack[Int]()
val sStack = Stack[Int]()
def appendTail(value: Int) {
fStack.push(value)
}
def deleteHead(): Int = {
if (sStack.isEmpty == false) {
return sStack.pop
} else {
while (fStack.size > 0) {
sStack.push(fStack.pop)
}
if (sStack.isEmpty == true) {
return -1;
} else {
return sStack.pop
}
}
}
}
/**
* Your CQueue object will be instantiated and called as such:
* var obj = new CQueue()
* obj.appendTail(value)
* var param_2 = obj.deleteHead()
*/
type CQueue struct {
inStack Stack
outStack Stack
}
type Stack []int
func (s *Stack) Push (value int) {
*s = append(*s, value)
}
func (s *Stack) Pop() int {
n := len(*s)
res := (*s)[n-1]
*s = (*s)[0:n-1]
return res
}
func Constructor() CQueue {
return CQueue{}
}
func (this *CQueue) AppendTail(value int) {
this.inStack = append(this.inStack, value)
}
func (this *CQueue) DeleteHead() int {
if len(this.outStack) != 0 {
return this.outStack.Pop()
} else if len(this.inStack) != 0 {
for (len(this.inStack) != 0){
this.outStack.Push(this.inStack.Pop())
}
return this.outStack.Pop()
}
return -1
}
/**
* Your CQueue object will be instantiated and called as such:
* obj := Constructor();
* obj.AppendTail(value);
* param_2 := obj.DeleteHead();
*/