公司概況

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公司規模約 50 人，其中約 30 位工程師。公司主要產品是在東南亞提供廉價網路服務。

第一輪人資電話面試

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本關約進行半小時 Culture Fit 審核。

第二輪線上技術測驗

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總共 2 題 HackerRank 題目，時間限制 120 分鐘，第二題限定使用 Java。

1. Roll The String

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A single roll operation on a string is a circular increment of each character by one. Looking at the English alphabet, characters in the range ascii[a-z], a becomes b, b becomes c, and z becomes a.

Given an array of integers named roll, perform a roll operation on the first roll[i] characters of s for each element i in the array. Given a zero indexed string, an operation roll[i] affects characters at positions 0 through (roll[i]-1).

Example

s = 'abz'

roll = [3, 2, 1]

Perform the following sequence of operations:

• roll[0] = 3: Roll all three characters so 'abz' becomes 'bca'.
• roll[1] = 2: Roll the first two characters so 'bca' becomes 'cda'.
• roll[2] = 1: Roll the first character so 'cda' becomes 'dda'.

After performing the operations, the final value of s is 'dda'.

Function Description

Complete the function rollTheString in the editor below.

rollTheString has the following parameter(s):

• string s: the string to operate on
• int roll[n]: an array of integers indicating the number of items in s to roll

Returns:

• string: the resulting string after all roll operations have been performed

Constraints

• Each character in s is a character in the range ascii[a-z].
• $1 \leqslant$ length of s $\leqslant 10^5$
• $1 \leqslant n \leqslant 10^5$
• $1 \leqslant$ roll[i] $\leqslant$ length of s, where $0 \leqslant i \lt n$.

2. Shape Inheritance

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The area and perimeter of different geometric shapes like rectangle, circle, or square are calculated using different mathematical formulae.

Create the following three classes:

1. The Rectangle class should implement the Shape interface. It should have two class variables of float type, length and, width. Also, it should implement the following methods:

   • Rectangle(float new_length, float new_width): sets the class variables, length = new_length and width = new_width respectively.
   • float getArea(): returns the result of length $\times$ width, the area of the rectangle. Also prints "Finding area of rectangle with length = {length} and width = {width}", where {length} and {width} are the respective values of class variables length and width.
   • float getPerimeter(): returns the result of 2 $\times$ (length + width), the perimeter of the rectangle. Also prints "Finding perimeter of rectangle with length = {length} and width = {width}".
   • String toString(): returns the string "Rectangle = [length: {length}, width: {width}, area: {area}, perimeter: {perimeter}]".

   Note: {length} and {width} respectively represent the class variables length and width. {area} and {perimeter} respectively represent the area and perimeter of the rectangle. For example, given that length = 2 and width = 3, calling the method toString() will return "Rectangle = [length: 2.0, width: 3.0, area: 6.0, perimeter: 10.0]".

2. The Square class that should inherit the Rectangle class and should implement the following methods:

   • Square(float side): sets the variables of Rectangle class, length = side and width = side respectively.
   • float getArea(): returns the result of length $\times$ width that denotes the area of the square. Also prints "Finding area of square with side = {length}"
   • float getPerimeter(): returns the result of 4 $\times$ length that denotes the perimeter of the square. Also prints "Finding perimeter of square with side = {length}"
   • String toString(): returns the string "Square = [side: {length}, area: {area}, perimeter: {perimeter}]".

   Note: {length} represents the variable length of Rectangle class. {area} and {perimeter} respectively represent the area and perimeter of the square. For example, given that side = 2, calling the method toString() will return "Square = [side: 2.0, area: 4.0, perimeter: 8.0]".

3. The Circle class that implements the Shape interface. It should have a class variable, radius. Also, it should implement the following methods:

   • Circle(float new_radius): sets the float type variable of Circle class, radius = new_radius.
   • float getArea(): returns the result of 3.14 $\times$ radius $\times$ radius that denotes the area of the circle. Also prints "Finding area of circle with radius = {radius}".
   • float getPerimeter(): returns the result of 6.28 $\times$ radius that denotes the perimeter of the circle. Also prints "Finding perimeter of circle with radius = {radius}".
   • String toString(): returns the string "Circle = [radius: {radius}, area: {area}, perimeter: {perimeter}]".

   Note: {radius} represents the variable radius of Circle class. {area} and {perimeter} respectively represent the area and perimeter of the circle. For example, given that radius = 1, calling the method toString() will return "Circle = [radius: 1.0, area: 3.14, perimeter: 6.28]".

The locked stub code in the editor provides the definition of the Shape interface. It also validates the implementation of Rectangle, Square, and Circle classes.

Constraints

• $1 \lt$ length, width, side, radius $\lt 10^2$

總結

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人資在照會當下並未說明技術前測有限定語言，因此在無預警情況下被迫使用 Java 進行 HackerRank 測驗，並於測驗隔日隨即收到感謝信。個人認為人資非常失職，甚至覺得被洗了業績，詢問後未得到回覆，整體體驗非常糟糕且差勁，希望欲投此間公司的朋友慎重考量。

面試結果及時程

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• 2021/09/30 第一輪人資電話面試
• 2021/10/05 第二輪線上技術測驗
• 2021/10/06 感謝信

附錄：第二輪線上技術測驗題目參考解答

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1. Roll The String

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以下解法為面試當下所寫，並非最優解。

#!/bin/python3

import math
import os
import random
import re
import sys

#
# Complete the 'rollTheString' function below.
#
# The function is expected to return a STRING.
# The function accepts following parameters:
#  1. STRING s
#  2. INTEGER_ARRAY roll
#

def rollTheString(s, rolls):
    n = len(s)
    roll_counts = [0] * n

    alphbets = 'abcdefghijklmnopqrstuvwxyz'
    alphbet_map = {a: i for i, a in enumerate(alphbets)}

    for roll in rolls:
        for i in range(roll):
            roll_counts[i] += 1

    results = []
    for i, roll_count in enumerate(roll_counts):
        original_alphabet = s[i]
        k = alphbet_map[original_alphabet]
        rolled_alphabet = alphbets[(k + roll_count) % 26]
        results.append(rolled_alphabet)

    return ''.join(results)

if __name__ == '__main__':
    # ...

參考 Roll the characters of string - GeeksforGeeksopen_in_new 之後重新整理出時間複雜度為 $O(n)$ 的解法：

def rollTheString(s, rolls):
    s_len = len(s)
    rolls_len = len(rolls)
    roll_counts = [0] * s_len

    for roll in rolls:
        roll_counts[roll - 1] += 1

    for i in range(rolls_len - 2, -1, -1):
        roll_counts[i] += roll_counts[i + 1]

    alphbets = 'abcdefghijklmnopqrstuvwxyz'
    alphbet_map = {a: i for i, a in enumerate(alphbets)}

    results = []
    for i, roll_count in enumerate(roll_counts):
        original_alphabet = s[i]
        k = alphbet_map[original_alphabet]
        rolled_alphabet = alphbets[(k + roll_count) % 26]
        results.append(rolled_alphabet)

    return ''.join(results)

assert rollTheString('a', [1]) == 'b'
assert rollTheString('aa', [1, 1]) == 'ca'
assert rollTheString('bca', [1, 2, 3]) == 'eeb'
assert rollTheString('zcza', [1, 1, 3, 4]) == 'debb'

2. Shape Inheritance

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import java.util.Scanner;

interface Shape {
    float getArea();
    float getPerimeter();
    String toString();
}

/*
 * Write the implementations of the Rectangle, Square, and Circle classes.
 */

public class Solution {
    private static final Scanner INPUT_READER = new Scanner(System.in);

    public static void main(String[] args) {
        String[] lengthWidth = INPUT_READER.nextLine().split(" ");
        float length = Float.parseFloat(lengthWidth[0]);
        float width = Float.parseFloat(lengthWidth[1]);

        float side = Float.parseFloat(INPUT_READER.nextLine());
        float radius = Float.parseFloat(INPUT_READER.nextLine());

        Shape rectangle = new Rectangle(length, width);
        Rectangle square = new Square(side);
        Shape circle = new Circle(radius);

        System.out.println("====================================");
        System.out.println("Finding area and perimeter of shapes");
        System.out.println("====================================");

        System.out.println("Area = " + rectangle.getArea() + " and Perimeter = " + rectangle.getPerimeter() + "\n");
        System.out.println("Area = " + square.getArea() + " and Perimeter = " + square.getPerimeter() + "\n");
        System.out.println("Area = " + circle.getArea() + " and Perimeter = " + circle.getPerimeter() + "\n");

        System.out.println("=========================");
        System.out.println("Printing shapes as string");
        System.out.println("=========================");

        System.out.println(rectangle.toString());
        System.out.println(square.toString());
        System.out.println(circle.toString());
    }

    public static class Rectangle implements Shape {
        float length;
        float width;

        public Rectangle(float new_length, float new_width) {
            this.length = new_length;
            this.width = new_width;

        }

        @Override
        public float getArea() {
            System.out.println("Finding area of rectangle with length = " + this.length + " and width = " + this.width);
            return this._getArea();
        }

        @Override
        public float getPerimeter() {
            System.out.println("Finding perimeter of rectangle with length = " + this.length + " and width = " + this.width);
            return _getPerimeter();
        }

        @Override
        public String toString() {
            return "Rectangle = [length: " + this.length + ", width: " + this.width + ", area: " + _getArea() + ", perimeter: " + _getPerimeter() + "]";
        }

        protected float _getArea() {
            return this.length * this.width;
        }

        protected float _getPerimeter() {
            return (this.length + this.width) * 2;
        }
    }

    public static class Square extends Rectangle {
        public Square(float side) {
            super(side, side);
        }

        @Override
        public float getArea() {
            System.out.println("Finding area of square with side = " + this.length);
            return super.getArea();
        }

        @Override
        public float getPerimeter() {
            System.out.println("Finding perimeter of square with side = " + this.length);
            return super.getPerimeter();
        }

        @Override
        public String toString() {
            return "Square = [side: " + this.length + ", area: " + _getArea() + ", perimeter: " + _getPerimeter() + "]";
        }
    }

    public static class Circle implements Shape {
        float radius;

        public Square(float new_radius) {
            this.radius = new_radius;
        }

        @Override
        public float getArea() {
            System.out.println("Finding area of circle with radius = " + this.radius);
            return this._getArea();
        }

        @Override
        public float getPerimeter() {
            System.out.println("Finding perimeter of circle with radius = " + this.radius);
            return _getPerimeter();
        }

        @Override
        public String toString() {
            return "Circle = [radius: " + this.radius + ", area: " + _getArea() + ", perimeter: " + _getPerimeter() + "]";
        }

        protected float _getArea() {
            return (float)3.14 * this.radius * this.radius;
        }

        protected float _getPerimeter() {
            return (float)6.28 * this.radius;
        }
    }