Old Mission Capital Internship & New Grad QT OA

Posted on November 20, 2025:

Overview

Old Mission Capital is one of the few firms that offers a winter Quantitative Trading internship. The program takes place in January and lasts for about three weeks.

I heard that they only hire around four interns per cohort, so the program is extremely competitive.

The OA consisted of three sections:

1. Math
2. Behavioral Essay
3. Coding

Math

• Time: 25 minutes
• Number of Questions: 20

From what I remember, the first 10 questions were moderately difficult problems covering topics such as probability and expected value.

The last 10 questions were divided into three larger game-based problems. Each problem introduced a game scenario and asked several related questions, such as:

• Calculating probabilities under different scenarios
• Computing expected values
• Determining the probability of winning the game
• Analyzing different possible game outcomes

This section was very time-constrained.

My advice would be to move on immediately after finishing each question instead of spending time checking your answers.

Behavioral Essay

• Time: 5 minutes

The essay asked you to explain:

• Why Old Mission Capital?
• Why Quantitative Trading?

I don't think this section is necessarily a major screening factor, but you still need to provide reasonable answers within the five-minute limit.

Coding

• Time: 20 minutes
• Number of Questions: 1

There was only one coding problem, and the difficulty was around LeetCode Easy level.

Overall, the coding section was fairly straightforward compared with the math section.

Posted on 2023 Aug, 15. For 2024 summer quant trader intern OA

Math / Probability

1. There are N socks in a drawer, including 3 red socks. Two socks are drawn at random. If the probability that both socks are red is 50%, how many socks are there in total?

2. On an 8 × 8 chessboard, two pieces are placed uniformly at random. What is the probability that the two pieces are not in the same row or the same column?

There were also many conditional probability questions.

# Old Mission Capital 2024 SWE New Grad OA posted in Aug 2023 

## Overview

The OA consisted of two main parts:

1. **Multiple-choice technical questions**
2. **Coding questions**

## Multiple-Choice Questions

There were around **30 to 45 multiple-choice questions**, and the candidate found this section very difficult.

Topics included:

- Systems
- Latency
- Linux
- C++
- Python

Some questions provided several **code snippets** and asked which one was correct.

Overall, this section was highly technical and covered a broad range of systems and programming topics.

## Coding Question 1

You are given two strings, `a` and `b`.

First, find all possible anagrams that can be formed from string `a`, and all possible anagrams that can be formed from string `b`.

Then, among the **longest valid anagrams** of `a` and `b`, choose the ones with the **smallest lexicographical order**.

Using those two anagrams, construct the **longest possible palindrome-like anagram** and return it.

If both selected anagrams have odd lengths, you may only choose the middle character from **one** of the two anagrams.

### Example

```text
a = "abaa"
b = "ccca"

Possible anagrams:

For a: [aaa, aba]
For b: [cac, ccc]

Choose:

aaa
cac

Combine them to form:

aaccaa

Return:

aaccaa

Coding Question 2

You are given:

• A list of customers
• A list of shops

Each customer has a list of exactly n required items.

Each shop has a list of exactly m available items.

At most 2 shops can be open at the same time.

A customer is considered satisfied if all of the items they need can be purchased from the currently open shops.

Return the maximum number of customers that can be satisfied.

Example

customers = [
  [1, 2],
  [1, 5]
]

shops = [
  [1, 3, 4, 5],
  [2, 4, 6, 8],
  [1, 3, 4, 6]
]

Output:

2

Explanation

If we open Shop 1 and Shop 2, the union of their available items is:

[1, 2, 3, 4, 5, 6, 8]

This is enough to satisfy both customers.

Therefore, the answer is:

2

Constraints

• The number of customers is large.
• The number of shops is large.
• m and n are relatively small.

Posted in 2022 September for 2023 Old Mission NG:

Posted in 2021 October for 2022 New Grad I think:

Multiple-Choice Questions

The first section consisted of 30 multiple-choice questions covering a wide range of topics, including:

• Algorithm time complexity
• Space complexity
• Linux commands and operations
• C++ syntax
• Python syntax
• Logic questions
• Other miscellaneous computer science topics

The questions covered a very broad range of material.

Coding 1: balanced string
coding 2: recover matrix

Another one Posted in 2021 October for 2022 New Grad I think:
coding 1: Balanced string
coding 2: LC 1253

Posted in September 2021 for New Grad

Part 1: Probability and Statistics

Part 1 consisted of more than 10 probability and statistics questions.

The calculations were somewhat heavy, so time management was important.

Part 2: Gambling / Game Probability

Part 2 included several gambling-style probability questions, and the calculations were also fairly involved.

The assessment introduced several different games.

For one of the games:

• The dealer draws two cards and tells you the values of both cards.
• You then decide how much you want to bet.
• The dealer draws a third card.

The payoff works as follows:

• If the third card falls strictly between the first two cards, you win an amount equal to your bet.
• If the third card is equal to either of the first two cards, you lose 2× your bet.
• If the third card falls outside the range of the first two cards, you lose 1× your bet.

The questions asked how much you would be willing to bet for different combinations of the first two cards.

Most of the questions in this section followed a similar game-based probability and expected value format.

Part 3: Pandas Data Processing

Part 3 focused on data processing with Pandas.

The main concept tested was the use of:

• groupby

The task was somewhat tricky and required careful handling of the data transformation logic.

GOOD LUCK!