题解 | #【模板】栈#

import java.util.Scanner

fun main(args: Array<String>) {
    val read = Scanner(System.`in`)
    val size = read.nextLine().toInt()
    val stackAb1 = StackAb1(size)
    while (read.hasNextLine()) {
        val lineArr = read.nextLine().split(" ")
        if (lineArr[0] == "push") {
            stackAb1.push(lineArr[1].toInt())
        } else if (lineArr[0] == "pop") {
            stackAb1.pop()
        } else {
            stackAb1.top()
        }
    }
}

class StackAb1(size: Int) {
    private lateinit var tempArray: IntArray
    private var top = 0

    init {
        if (size in 1..100000) {
            tempArray = IntArray(size)
        } else {
            println("error")
        }
    }

    fun push(value: Int) {
        if (top < tempArray.size) {
            tempArray[++top] = value
        } else {
            println("error")
        }
    }

    fun pop() {
        if (top > 0) {
            println(tempArray[top--])
        } else {
            println("error")
        }
    }

    fun top() {
        if (top > 0) {
            println(tempArray[top])
        } else {
            println("error")
        }
    }
}