这篇 Microsoft 面经 并不是传统意义上的“题目汇总”，而是 ProgramHelp 在最近一段时间里，连续协助多位同学完成 Microsoft Online Assessment 后，整理出来的一份真实观察记录。
有意思的是，这一轮微软 OA 并没有明显提升算法难度，但通过率却并不高。
问题不在“会不会做题”，而在是否理解微软真正想通过 OA 判断什么。
Microsoft OA流程回顾
从 ProgramHelp 近期协助的多批 Microsoft Online Assessment 来看，微软 OA 的整体形态相对稳定，但对细节的要求一直被低估。
微软 OA 并不是一场比谁算法更难的测试，而是一轮非常典型的“基础能力 + 稳定度筛选”。
OA 的基本形式
在大多数软件类岗位（SDE / New Grad / Intern）中，微软 OA 通常具备以下特征：
- 在线完成，不允许使用本地 IDE
- 总时长一般在 75–90 分钟区间
- 题目以 2–3 道编程题为主
- 个别批次会夹杂少量逻辑或数学思维题
整体节奏偏紧，但并不追求极限速度，而是要求在有限时间内交付可运行解法。
题型分布
根据这次以及往届同学反馈，题型主要分布：
- String processing 占大头
- 常见考点：consecutive characters、palindrome、lexicographic order。
- 本质就是对字符串扫描、分段、比较，难度中等，但细节多。
- Array & Graph 基础题
- 偏向常规算法，比如 array manipulation、BFS/DFS。
- 不会出太怪的题，主要看基本功扎实不扎实。
- 经典 patterns 高频考
- Two Sum 系列
- Sliding Window
- Greedy choice（interval/substring 类型）
- 动态规划偶尔会考，但一般不深。
Microsoft OA 真题分享
I. Programming Problems (2 Questions)
Programming Problem 1: Longest Valid Parentheses
Problem Description
Given a string containing only ‘(‘ and ‘)’, find the length of the longest valid (well-formed) parentheses substring. A valid parentheses substring must have properly paired and nested parentheses. For example, “()()” and “(())” are valid parentheses substrings, while “())” and “(()” are invalid.
Examples
- Example 1: Input: s = “(()”, Output: 2. Explanation: The longest valid parentheses substring is “()”, with a length of 2.
- Example 2: Input: s = “)()())”, Output: 4. Explanation: The longest valid parentheses substring is “()()”, with a length of 4.
- Example 3: Input: s = “”, Output: 0.
Requirements
- Time complexity must not exceed O(n) (where n is the length of the string).
- Space complexity must not exceed O(n).
Programming Problem 2: Task Scheduler
Problem Description
Given a character array representing tasks that a CPU needs to execute. Each letter represents a different type of task. Tasks can be executed in any order, and each task takes 1 unit of time to complete. At any unit of time, the CPU can either execute a task or be in an idle state.
There must be a cooldown period of integer length n between two tasks of the same type. That is, there must be at least n consecutive units of time where the CPU is either executing a different task or in an idle state.
Calculate the minimum time required to complete all tasks.
Examples
- Example 1: Input: tasks = [“A”,”A”,”A”,”B”,”B”,”B”], n = 2, Output: 8. Explanation: One possible execution order is A -> B -> (Idle) -> A -> B -> (Idle) -> A -> B, with a total time of 8 units.
- Example 2: Input: tasks = [“A”,”A”,”A”,”B”,”B”,”B”], n = 0, Output: 6. Explanation: There is no cooldown period, so all tasks can be executed in sequence directly, with a total time of 6 units.
- Example 3: Input: tasks = [“A”,”A”,”A”,”A”,”A”,”A”,”B”,”C”,”D”,”E”,”F”,”G”], n = 2, Output: 16. Explanation: One possible execution order is A -> B -> C -> A -> D -> E -> A -> F -> G -> A -> (Idle) -> (Idle) -> A -> (Idle) -> (Idle) -> A, with a total time of 16 units.
Requirements
- Time complexity must not exceed O(m) (where m is the length of the task list).
- Space complexity must not exceed O(26) (since tasks only consist of 26 uppercase English letters).
II. Logical/Mathematical Mini-Questions (5 Questions)
Mini-Question 1: Logical Reasoning
A Microsoft team has three engineers: Jia, Yi, and Bing, each responsible for one of three areas: Frontend, Backend, and Algorithms. The following information is known:
- Jia is not responsible for Frontend;
- Yi is not responsible for Backend;
- The engineer in charge of Algorithms and the engineer in charge of Frontend are colleagues and have different genders (assuming the three have different genders, and Jia is male).
Which area is Bing responsible for?
A. Frontend B. Backend C. Algorithms D. Cannot be determined
Mini-Question 2: Mathematical Calculation
There is a positive integer array with all distinct elements. When each element in the array is multiplied by 2, the number of elements in the intersection of the new array and the original array is half the length of the original array, and the length of the original array is even. It is known that the smallest element in the original array is 1 and the largest is 10. What could be the length of the original array?
A. 2 B. 4 C. 6 D. 8
Mini-Question 3: Probability Problem
A bag contains 5 red balls and 3 white balls. One ball is randomly drawn from the bag each time, and the ball is not put back after drawing. Two balls are drawn consecutively. What is the probability that the first ball drawn is red and the second is white?
A. 15/56 B. 15/28 C. 5/14 D. 3/14
Mini-Question 4: Logical Thinking
In a software development project, four modules (A, B, C, D) need to be completed, with dependency relationships between the modules as follows:
- Module B can only start after Module A is completed;
- Module D can only start after both Modules B and C are completed;
- Module C can start at any time (no pre-dependencies).
If the development time for each module is 2 days, and only one module can be developed at a time, what is the minimum time required to complete all modules?
A. 6 B. 8 C. 10 D. 12
Mini-Question 5: Mathematical Analysis
It is known that the three sides of a right-angled triangle are all integers, and the length of one of the right-angled sides is 12. What is the maximum possible perimeter of this right-angled triangle?
A. 84 B. 90 C. 96 D. 102
不在孤军奋战：带你轻松通关微软OA
微软的 OA 看似套路，其实细节和陷阱不少。很多同学卡在边界条件或者时间分配，一不小心就影响整体表现。其实只要方向正确，OA 完全是可以“拿捏”的一关。
如果你不想一个人硬扛，Programhelp 可以给到实时的OA远程无痕助攻：
实时语音提醒，遇到卡点直接点拨思路；
联机代写支持，代码细节全程无痕衔接；
提前 mock 练习，模拟真实考试节奏。
有了助攻，不仅能节省时间，还能把握住微软这类高重复率的 OA。
