Karat VO 面试真题解析：按年份统计收入计算器（Income Calculator by Year）

Task:

• Implement the following problem
• Write a unit test for the implementation

We want to implement an income calculator that, given a compensation package and a start date, returns the income earned in each year up to the current date.

The input is:

• Start date (SimpleDate)
• Base salary per year (int)
• RSU per year (int)
• Sign on bonus, only once (int)

SimpleDate is my own implementation of Date. It has these fields:

• SimpleDate:
• month: int
• year: int

You can also use SimpleDate.now() to get the current date.

Example: Given these values

• Base salary: 120,000
• Annual RSU: 60,000
• One-time Sign on: 25,000
• Start date: 02/2021
• Current date: 02/2023

The calculator should return:

• 2021: 190,000 (11 months income, including February plus sign on)
• 2022: 180,000 (12 months income)
• 2023: 15,000 (only January, excluding February)

这道题要求实现一个按年份拆分的收入计算器：给定入职月份、年 base salary、每年 RSU 以及一次性 sign-on bonus，统计从开始日期到当前日期之间每一年的总收入。核心做法是按年份和月份区间逐段计算，先处理起始年的剩余月份、再处理中间完整年份、最后处理当前年的已过去月份；其中 sign-on bonus 只在开始年份计入一次。实现时要特别注意月份边界，例如示例中从 02/2021 到 02/2023，2021 年只算入职后的 11 个月并加上签约奖金，2022 年按完整 12 个月计算，2023 年只算 1 月。