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Shopify·Data Scientist·Technical Phone Screen·Intermediate

Intermediate
May 2026

Summary

Shopify Data Scientist interview that was basically a pattern recognition gauntlet. Four sequence/grid puzzles back to back, which felt more like a math olympiad warm-up than a data science screen. Not what I was expecting.

Questions Asked (4)

Q1

Find the next number in the sequence 2, 3, 5, 9, 17, 33, and explain your reasoning.

Algorithms & Data Structures
Author's notes

Each term doubles the previous one and subtracts 1, so 33 times 2 minus 1 gives 65.

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AI HintsAI Generated

Suggested Approach

First, identify the pattern by examining differences between consecutive terms: 1, 2, 4, 8, 16, which are powers of 2. Then, use this to predict the next difference and compute the next term. Finally, explain the reasoning clearly and consider alternative patterns.

Pro tip: After finding the pattern, briefly mention that you'd validate it with more terms or consider if other patterns exist, showing thoroughness. Also, relate it to how you'd approach pattern recognition in data science, such as time series analysis.

1. Observe the sequence

Write down the given numbers: 2, 3, 5, 9, 17, 33. Look for simple relationships between consecutive terms.

2. Calculate differences

Compute the differences: 3-2=1, 5-3=2, 9-5=4, 17-9=8, 33-17=16. Notice that the differences are powers of 2: 2^0, 2^1, 2^2, 2^3, 2^4.

3. Identify the pattern

The differences double each time, so the next difference should be 32 (2^5). Alternatively, each term is previous term plus a power of 2, or each term is 2*previous term - 1.

4. Compute the next term

Add the next difference (32) to the last term (33) to get 65. Verify using the alternative pattern: 2*33 - 1 = 65.

5. Explain reasoning

Clearly state the pattern and how you arrived at the answer. Mention that you checked multiple perspectives to ensure consistency.

Key Points to Mention

  • Differences between consecutive terms: 1, 2, 4, 8, 16 (powers of 2)
  • Pattern: each term is previous term plus a power of 2, or each term is 2*previous term - 1
  • Next difference is 32, so next term is 33+32=65
  • Verification: 2*33 - 1 = 65
  • Generalization: a_n = 2^(n-1) + 1 for n>=1 (with a_1=2)
  • Relevance to data science: pattern recognition, sequence prediction, time series analysis

AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.

Q2

Identify the next two values in the sequence 1, 4, 2, 8, 4, 16, 8, 32, ?, ?

Algorithms & Data Structures
Author's notes

Two interleaved sequences running in parallel: one doubles each step (1, 2, 4, 8...) and the other does the same but offset (4, 8, 16, 32...).

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AI HintsAI Generated

Suggested Approach

First, scan the sequence for alternating patterns or operations. Notice that odd-positioned terms (1,2,4,8) double each time, while even-positioned terms (4,8,16,32) also double. Then extend each subsequence to find the next two values.

Pro tip: Verbalize your reasoning step-by-step, as interviewers value clear thought process over just the answer. Also, briefly mention that such patterns can be modeled as two interleaved geometric sequences, showing your data science mindset.

1. Observe the sequence

Write down the given numbers and look for simple relationships like addition, multiplication, or alternation.

2. Identify alternating patterns

Separate the sequence into odd and even positions. Check if each subsequence follows a consistent rule.

3. Determine the rule for each subsequence

For odd positions: 1,2,4,8 → multiply by 2 each time. For even positions: 4,8,16,32 → multiply by 2 each time.

4. Extend the subsequences

The next odd-position term after 8 is 16; the next even-position term after 32 is 64.

5. Verify and present

Check that the pattern holds for all given terms and state the next two values clearly: 16 and 64.

Key Points to Mention

  • Alternating pattern recognition
  • Geometric progression with common ratio 2
  • Interleaved sequences
  • Systematic verification of pattern
  • Clear communication of reasoning
  • Relevance to data science: pattern recognition in sequences

AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.

Q3

What comes next in the sequence 1, 3, 7, 15, 31, and why?

Algorithms & Data Structures
Author's notes

Each term is 2 to the power of n minus 1, so the next is 63.

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AI HintsAI Generated

Suggested Approach

Start by examining the differences between consecutive terms to identify the pattern, then generalize it to find the next term. Clearly state the rule and verify it with the given sequence before providing the answer.

Pro tip: After finding the answer, mention that this is a geometric progression with ratio 2 plus 1, and relate it to binary representation or exponential growth, which is common in data science contexts like algorithm complexity or growth models.

1. Identify the pattern

Calculate the differences between consecutive terms: 3-1=2, 7-3=4, 15-7=8, 31-15=16. Notice that the differences double each time.

2. Formulate the rule

Express the pattern as a recurrence relation: each term is twice the previous term plus 1 (a_n = 2*a_{n-1} + 1). Alternatively, recognize that each term is one less than a power of 2: 1=2^1-1, 3=2^2-1, 7=2^3-1, etc.

3. Apply the rule to find the next term

Using the recurrence, the next term is 2*31 + 1 = 63. Using the power of 2 pattern, the next term is 2^6 - 1 = 63.

4. Verify and explain

Check that 63 fits the pattern: 63-31=32, which is double the previous difference (16). Also, 63 = 2^6 - 1, continuing the sequence.

5. Connect to data science context

Mention that such sequences often appear in algorithm analysis (e.g., number of nodes in a perfect binary tree of height h is 2^{h+1}-1) or in exponential growth models, demonstrating relevance to the role.

Key Points to Mention

  • The sequence follows the pattern a_n = 2^n - 1 for n=1,2,3,...
  • The differences between consecutive terms are powers of 2: 2, 4, 8, 16, 32.
  • The recurrence relation a_n = 2*a_{n-1} + 1.
  • The next term is 63.
  • Connection to binary representation: each term in binary is a string of n ones (e.g., 1, 11, 111, 1111, 11111, 111111).
  • Relevance to data science: exponential growth, algorithm complexity, or binary tree properties.

AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.

Q4

In a 3x3 grid where the rows are [7, 4, 11], [5, 9, 14], and [?, 13, 18], find the missing value and describe the rule governing each row.

Algorithms & Data Structures
Author's notes

Each row sums the first two values to get the third: 7+4=11, 5+9=14, so ?+13=18 means the missing number is 5.

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AI HintsAI Generated

Suggested Approach

First, identify the pattern within each row by comparing the first two numbers to the third. Then, apply the discovered rule to the third row to find the missing value, and clearly articulate the rule for each row.

Pro tip: After finding the answer, briefly mention how you would validate the pattern with additional data or edge cases, showing a data scientist's rigor.

1. Examine the given rows

Look at the first two rows to see how the third number is derived from the first two. For example, in row 1: 7 + 4 = 11; in row 2: 5 + 9 = 14.

2. Identify the pattern

Notice that in each row, the third number is the sum of the first two numbers. This is a consistent rule across the rows.

3. Apply the pattern to the third row

Use the rule to find the missing value: ? + 13 = 18, so ? = 5.

4. Describe the rule

State clearly that the rule is: the third number in each row equals the sum of the first two numbers.

5. Verify and generalize

Check that the rule holds for all rows, and consider if there are alternative patterns or if the rule could be extended to columns or other structures.

Key Points to Mention

  • The rule is addition: third number = first number + second number.
  • The missing value is 5.
  • Consistency of the pattern across all rows.
  • Potential alternative patterns (e.g., differences, multiplication) and why addition is the simplest.
  • How to validate the pattern with additional data or edge cases.
  • The importance of clearly stating assumptions and the reasoning process.

AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.