What Real Interview Questions Reveal About Tech Hiring: Algorithms, System Design, and More

Background: an EE communications PhD who switched careers after nearly four years at a communications chip company.

Recruitment approach: directly asked friends for recruiter emails, sent messages, and scheduled casual phone screens that often led to onsite interviews. Occasionally used internal referrals, which responded more slowly but still yielded results.

Facebook interview:

Binary string addition; follow‑up on arbitrary bases up to hexadecimal.

Maximum depth of a tree (warm‑up).

Find a number in a rotated sorted array.

Factor combinations of a number (e.g., 24 = 2×12, 2×2×3, …).

Onsite experience: a Chinese candidate helped secure the onsite round.

Additional Facebook questions:

Find the first bad version given an isGood(version) API.

BST inorder traversal.

Convert a string to a floating‑point number (stof).

Print a tree column‑wise without using a hashmap; store node horizontal distances in a vector, one‑pass, without pre‑computing tree width.

System design: query the number of users matching a combination of large fields (age, gender, hobbies, etc.).

LinkedIn interview questions:

Maximum point on a line, handling non‑integer coordinates (requires custom hashmap compare).

Special container supporting add, remove, and removeRandom in O(1) using an array plus hashmap.

K‑way sort given a stream iterator (vector<stream>).

Product of all other elements in an array, considering cases with one or two zeros.

Implement memmove(void* src, void* dest).

System design: tiny URL service.

Data‑center replication: copy data from one data center to another without affecting functionality.

Google interview questions:

Find all rotation‑symmetric numbers less than N digits (e.g., 16891 → 16891).

Reverse an integer (12345 → 54321).

Given a target string and a list of strings, find the longest string that has the target as a prefix; use a trie storing each node’s information.

Integer array increment (add one).

Given a grid of colors, a point and its color, compute the perimeter of the region with the same color.

Generate all Morse code sequences under length constraints, where short "*" counts as one unit and long "—" counts as two; identify a bug in the code (typical combinatorial problem).

Design a Chromecast system to determine which apps are supported, involving cloud services that provide appID, deviceID, and cache design.