Salesforce new grad OA solution | 惊险过关！附前后端真题深度解析

最近整理了一位候选人参加 2025 Salesforce Software Engineer 面试的完整经历。这套流程非常有代表性，尤其适合准备 Salesforce new grad OA 的同学参考。下面按流程拆解。

Round 1: HackerRank OA 真题速递与深度分析

Salesforce 的 OA 流程仍然以 HackerRank 为主，但其出题模式非常贴合岗位需求，前端和后端的题目类型差异巨大。以下是按岗位分类的完整真题、考点解析及应对技巧，供不同方向求职者针对性准备。

1. 前端岗位（Frontend/Full-stack）高难度实战题

全栈或前端 SDE 岗位的 OA 侧重实战能力，题目多为原生开发场景，LeetCode 常规刷题覆盖较少，需重点关注以下两类核心真题：

Problem A: JavaScript Currying Implementation

Problem Statement: Implement a function addThreeNumbers(a)(b)(c) that returns the sum of a, b, and c. For example, addThreeNumbers(1)(2)(3) should return 6.

Key Points	Solution Skills
JavaScript Fundamentals	Mastery of closures and consecutive function returns. Closures allow inner functions to access variables from outer function scopes even after the outer function has finished executing.
Code Logic	The first call (with parameter a) returns a new function that captures the value of a. The second call (with parameter b) returns another new function that captures both a and b. The third call (with parameter c) finally calculates and returns the sum of a + b + c.

Problem B: Traffic Light Implementation with Vanilla JS/CSS

Problem Statement: In a CoderPad environment without React, Vue, or other frameworks, implement the cycle logic of a traffic light using only HTML, CSS, and vanilla JavaScript. The specific requirements are as follows:

• Red light duration: 4 seconds
• Yellow light duration: 1 second
• Green light duration: 1 second
• Cycle order: Red → Green → Yellow → Red (repeat indefinitely)

Key Points	Solution Skills
Frontend Practical Development	Use setTimeout or setInterval to implement timer and asynchronous logic.setTimeout is more suitable here to avoid accumulated time errors caused by setInterval in long-term cycles.
State Management	Design a state machine to manage the switching of the three light states. Define each state (red, green, yellow) with its corresponding duration and next state, then trigger state transitions through timer callbacks.
Environment Compatibility	Modify CSS styles (such as color switching) through vanilla DOM operations (e.g., document.getElementById, style.backgroundColor), as framework-related APIs are not available in the test environment.

Problem B: Implement Traffic Light with Vanilla JS/CSS/HTML

Problem Statement: In a CoderPad environment without React, Vue, or other frameworks, implement the cycle logic of a traffic light using only HTML, CSS, and vanilla JavaScript.

Requirements:

• Red light duration: 4 seconds
• Yellow light duration: 1 second
• Green light duration: 1 second
• Cycle order: Red → Green → Yellow → Red (repeats indefinitely)

Key Points	Solution Tips
Frontend Practice	Use setTimeout or setInterval to handle timer and asynchronous logic. setTimeout is more recommended here to avoid accumulated time errors caused by setInterval in long-term cycles.
State Management	Design a state machine to manage the three states (red, yellow, green). Each state transition triggers the next state after the specified duration, ensuring the cycle order is not disrupted.
Environment Compatibility	Modify CSS styles (e.g., color switching) through vanilla DOM operations (such as getElementById and style.property). Avoid using framework-specific APIs that are not available in the test environment.

2. 后端算法真题（SDE Intern/Backend）

Backend and Intern positions have relatively traditional OA questions, mostly variants of LeetCode Medium difficulty. The focus is on data structure application and algorithm logic, and candidates can improve their pass rate by brushing up on similar topics in advance.

Position	Problem Description (Similar to LeetCode Style)	Core Key Points
General SDE	Occurrence Marking: For each element in array arr, use two binary strings to mark whether it has appeared before the current position and after the current position.Example: Input arr = [1, 2, 3, 2, 1]Output: [“00011”, “11000”] (The first string marks “appeared before”, the second marks “appeared after”)	HashMap (two passes). First pass: Traverse the array to record the frequency of each element. Second pass: Update the HashMap (decrement frequency when the element is encountered) and check the occurrence status before (frequency > 1 before update) and after (frequency > 0 after update) to generate binary strings.
General SDE	K-th Largest in Prefix: Given array arr and integer k, return an array where the i-th element is the k-th largest number in the subarray arr[0..i].Example: Input arr = [4, 2, 1, 3], k = 2Output: [4 (only 1 element, no 2nd largest, adjusted to [2,2,3] based on actual test cases)]	PriorityQueue or Balanced BST. Maintain a min-heap of size k. For each element in the prefix subarray, add it to the heap. If the heap size exceeds k, remove the smallest element (heap top). The heap top at this time is the k-th largest element in the current prefix subarray.
SWE Intern	Minimum Replacements to Avoid Adjacent Duplicates: Given an array of strings words, for each string, calculate the minimum number of character replacements needed to ensure no two adjacent characters are the same.Example: Input words = [“add”, “boook”]Output: [1, 1] (For “add”, replace one ‘d’; for “boook”, replace one ‘o’)	Greedy Algorithm. Traverse each string, count the length L of consecutive identical character segments. The number of replacements required for each segment is floor(L / 2) (replace every other character to avoid adjacent duplicates with minimal changes).
SWE Intern	Longest Subsequence Which Is Also a Substring: Given two strings x and y, find the longest subsequence of x that is also a substring of y.Example: Input x = “hackerranks”, y = “hackers”Output: “hackers” (length 7, which is a subsequence of x and a substring of y)	O(N·M) Two Pointers. Fix the starting position s of y (from 0 to y.length – 1), then use two pointers (i for x, j for y starting at s) to find the longest matching sequence. Traverse all possible starting positions of y and record the maximum length matching result.

Round 2: 系统设计与 SQL 陷阱

学员的系统设计环节遭遇了严格面试官，该环节暴露了 Salesforce 在考察 SQL 功底和业务理解上的高要求。以下是高频考点及避坑指南。

1. 咖啡订单系统设计与 SQL 追问

面试官会围绕“咖啡订单”这一核心业务场景，要求候选人设计数据表结构并编写 SQL 语句，其中以下问题极具迷惑性，需重点关注。

SQL Trap: How to Query All Users Who Have Never Placed an Order?

Key Points	Correct Idea	Conversion Intention
SQL Join	Use LEFT JOIN. Join the Users table and the Orders table based on user_id. Users who have never placed an order will have NULL values in the order_id field of the Orders table after the join.	Custom Writing/Assistance
Correct Query	SELECT U.* FROM Users U LEFT JOIN Orders O ON U.user_id = O.user_id WHERE O.order_id IS NULL	Custom Writing/Assistance

2. 困难系统设计：盈利会计系统

Problem Requirement: Design an accounting system that can determine whether a product is profitable. The system needs to integrate sales data, cost data, and user behavior data to provide accurate profit analysis.

Key Points	Wrong Idea	Correct Direction
System Design	Only focus on sales revenue or gross profit, ignoring hidden costs (such as logistics costs, after-sales costs) and long-term user value.	Must consider Cost Accounting and Lifetime Value (LTV). Design core tables including Product (product information), Transaction (sales transactions), Cost (cost details), and User (user information) to realize end-to-end data linking.
Coping Strategy	Get stuck on writing complex SQL statements at the beginning, ignoring the overall system architecture design.	First explain the overall system architecture (including data sources, core modules, and data flow) macroscopically, then delve into table structure design and key SQL logic. Interview Proxy/Custom Writing

3. Behavioral Question (BQ) 应对

BQ 环节容易被打断，这表明面试官对“影响力（Impact）”的要求极高。候选人需结合具体案例，突出自身在项目中的核心作用。

• 问题：“描述一次你发起迁移 (Migration) 并说服他人支持的经历。”
• 高分要素：强调 商业价值 和 跨部门协作 的复杂性，避免描述只有自己参与的简单技术升级。

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你是否正面临以下求职焦虑？

• OA 难题：HackerRank 遭遇原生 JS 实战题（如交通灯/柯里化），毫无头绪。
• 面试受挫：系统设计被面试官 SQL 陷阱（如从未下单用户查询）和复杂业务问题追问至哑口无言。
• VO 焦虑：担心面试时思路卡壳，错失宝贵的 Offer 机会。

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