Coding Interview Questions

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638 questions
547 companies
27 roles
Last updated Nov 2026

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Merge a stream of (timestamp, location, temperature) records with a stream of (timestamp, location, humidity) records, handling keys that appear in only one stream.
4 years ago
In pandas, compute the mean of a feature grouped by name, then the weighted mean of a feature grouped by name.
3 days ago
Write from scratch a class that reports the maximum of the last k values of a data stream.
+13 days ago
Implement the Newton-Raphson method.
3 days ago
Write a MapReduce algorithm for the closed-form OLS solution when the number of rows n is far too large for one machine, the number of features k is small and you have m machines.
3 days ago
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Given a string of lowercase English letters, count the ways to add one letter to it so that the result is a permutation of some palindrome.
4 years ago
Given a non-negative integer, return the largest number that can be formed by rearranging its digits. Example: 318 gives 831.
6 years ago
You get a compressed archive of log files and must report how many entries failed and how many nearly failed, with no status field. How do you explore, define failure and count?
6 years ago
Write an iterator that walks over all elements of a vector<vector<T>> in order.
3 days ago
Explain tail recursion.
3 days ago
Implement spreadsheet cells where a cell can be the sum of other cells, which can themselves be sums, and compute the sum of an array of cells.
3 days ago
Parse a spec that chains tasks serially with commas and in parallel with braces and semicolons, and output every nested call expression it expands to.
10 months ago
Write Python code that outputs all permutations of a list of integers, and analyse its time complexity.
3 days ago
In Python, estimate by Monte Carlo the probability of getting exactly 4 heads in 6 coin flips, without using any for-loops (i.e. vectorised).
3 days ago
Count the squares, not necessarily axis-aligned, formed by a list of points.
3 days ago
How would you compute a covariance matrix when the underlying data is too large to fit in memory?
3 days ago
You have three lists of n numbers. Choose one number from each so that the largest minus the smallest of the three is as small as possible. What algorithm do you use?
3 days ago
Implement a file reader in C++ that processes data in chunks, and handle exceptions correctly during the chunked processing.
10 months ago
Given a list of integers, return a new list with duplicates removed, keeping first-occurrence order. Example: [4,1,2,2,3,4] gives [4,1,2,3].
3 days ago
Players move right along a line toward an endpoint while a watcher freezes any player in its line of sight and flips direction at given times. How many players reach the end by time T?
3 days ago

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Coding Interview Questions

Merge a stream of (timestamp, location, temperature) records with a stream of (timestamp, location, humidity) records, handling keys that appear in only one stream.

In pandas, compute the mean of a feature grouped by name, then the weighted mean of a feature grouped by name.

Write from scratch a class that reports the maximum of the last k values of a data stream.

Implement the Newton-Raphson method.

Write a MapReduce algorithm for the closed-form OLS solution when the number of rows n is far too large for one machine, the number of features k is small and you have m machines.

Given a string of lowercase English letters, count the ways to add one letter to it so that the result is a permutation of some palindrome.

Given a non-negative integer, return the largest number that can be formed by rearranging its digits. Example: 318 gives 831.

You get a compressed archive of log files and must report how many entries failed and how many nearly failed, with no status field. How do you explore, define failure and count?

Write an iterator that walks over all elements of a vector<vector<T>> in order.

Explain tail recursion.

Implement spreadsheet cells where a cell can be the sum of other cells, which can themselves be sums, and compute the sum of an array of cells.

Parse a spec that chains tasks serially with commas and in parallel with braces and semicolons, and output every nested call expression it expands to.

Write Python code that outputs all permutations of a list of integers, and analyse its time complexity.

In Python, estimate by Monte Carlo the probability of getting exactly 4 heads in 6 coin flips, without using any for-loops (i.e. vectorised).

Count the squares, not necessarily axis-aligned, formed by a list of points.

How would you compute a covariance matrix when the underlying data is too large to fit in memory?

You have three lists of n numbers. Choose one number from each so that the largest minus the smallest of the three is as small as possible. What algorithm do you use?

Implement a file reader in C++ that processes data in chunks, and handle exceptions correctly during the chunked processing.

Given a list of integers, return a new list with duplicates removed, keeping first-occurrence order. Example: [4,1,2,2,3,4] gives [4,1,2,3].

Players move right along a line toward an endpoint while a watcher freezes any player in its line of sight and flips direction at given times. How many players reach the end by time T?

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