01. 이해
큐에서 제공하는 함수들을 가지고 스택의 내부 함수를 구현
02. 계획
push에서 queue처럼 작동하도록 미리 넣어두거나, pop할 때 queue처럼 빼지도록 해야하는데 peek을 간단히 구현하기 위해서는 넣을 때 제대로 넣어두는게 좋을 듯.
03. 실행
/**
* Runtime: 152 ms, faster than 83.72% of Kotlin online submissions for Implement Queue using Stacks.
* Memory Usage: 34.8 MB, less than 25.58% of Kotlin online submissions for Implement Queue using Stacks.
*/
class MyQueue() {
/** Initialize your data structure here. */
var stack = ArrayList<Int>()
val tempStack = ArrayList<Int>()
/** Push element x to the back of queue. */
fun push(x: Int) {
if (stack.isEmpty()){
stack.add(x)
}else {
for (i in 0 until stack.size) {
tempStack.add(stack.removeAt(stack.size -1))
}
stack.add(x)
while (tempStack.isNotEmpty()){
stack.add(tempStack.removeAt(tempStack.size - 1))
}
}
}
/** Removes the element from in front of queue and returns that element. */
fun pop(): Int {
return stack.removeAt(stack.size - 1)
}
/** Get the front element. */
fun peek(): Int {
return stack.last()
}
/** Returns whether the queue is empty. */
fun empty(): Boolean {
return stack.isEmpty()
}
}
/**
* Runtime: 172 ms, faster than 25.58% of Kotlin online submissions for Implement Queue using Stacks.
* Memory Usage: 34.8 MB, less than 20.93% of Kotlin online submissions for Implement Queue using Stacks.
*/
class MyQueue2() {
/** Initialize your data structure here. */
val stack1 = ArrayList<Int>()
val stack2 = ArrayList<Int>()
var front = 0
/** Push element x to the back of queue. */
fun push(x: Int) {
if (stack1.isEmpty()){
front = x
}
stack1.add(x)
}
/** Removes the element from in front of queue and returns that element. */
fun pop(): Int {
if (stack2.isEmpty()){
while (stack1.isNotEmpty()){
stack2.add(stack1.removeAt(stack1.size - 1))
}
}
return stack2.removeAt(stack2.size - 1)
}
/** Get the front element. */
fun peek(): Int {
if (stack2.isNotEmpty()){
return stack2.last()
}
return front
}
/** Returns whether the queue is empty. */
fun empty(): Boolean {
return stack1.isEmpty() && stack2.isEmpty()
}
}04. 회고
큐로 스택을 만드는 문제와 유사한 유형이었다. 메모리 성적이 좋지 않게 나오는건 arraylist를 사용해서일까?
Runtime: 164 ms, faster than 46.51% of Kotlin online submissions for Implement Queue using Stacks.
Memory Usage: 34.9 MB, less than 9.30% of Kotlin online submissions for Implement Queue using Stacks.
