How do I practice coding and algorithm questions?

Use PracHub's coding console to write, test, and debug your solutions in Python or JavaScript. View hints, test against sample inputs, and compare with official solutions.

What difficulty level is this coding question?

This is a Medium difficulty Coding & Algorithms question, commonly asked during Technical Screen rounds at Other.

What role is this question designed for?

This question is commonly asked for Data Scientist candidates at Other during technical interviews.

Implement multiplication without using the multiplication operator

Quick Overview

This question evaluates proficiency in bitwise arithmetic, integer overflow semantics, sign handling, and algorithmic efficiency for implementing multiplication without using multiplication or division operators.

Implement multiplication without using the multiplication operator

Company: Other

Role: Data Scientist

Category: Coding & Algorithms

Difficulty: Medium

Interview Round: Technical Screen

Implement int multiply(int a, int b) without using * or /. You may use +, −, bitwise operators, and shifts. Requirements: - Handle negatives, zero, and the corner case INT_MIN * −1. - Achieve O(log |b|) additions via shift‑and‑add (Russian peasant), not naive O(|b|) repeated addition. - Assume 32‑bit signed ints. First implement unchecked overflow (two’s‑complement wrap), then a safe version that saturates to INT_MAX/INT_MIN on overflow without using 64‑bit types. - Analyze time and space complexity and prove correctness for all sign combinations. - Provide unit tests: 0×x, 1×x, −1×x, powers of two, random pairs, INT_MAX×2, INT_MIN×2, INT_MIN×−1. Follow‑ups: how would you extend to big integers and compare with Karatsuba? What changes if the platform lacks arithmetic right shift?

Quick Answer: This question evaluates proficiency in bitwise arithmetic, integer overflow semantics, sign handling, and algorithmic efficiency for implementing multiplication without using multiplication or division operators.

Unchecked 32-bit Multiply Without *

Return a*b using shift-and-add with two-complement 32-bit wraparound.

Constraints

Inputs are Python literals matching the function signature.
Return a deterministic exact-match value.

Examples

Input: (3, 5)

Expected Output: 15

Explanation: Positive values.

Input: (-7, 6)

Expected Output: -42

Explanation: Negative sign.

Input: (2147483647, 2)

Expected Output: -2

Explanation: Wrap overflow.

Input: (0, -99)

Expected Output: 0

Explanation: Zero.

Hints

Choose a representation that makes the requested operation direct.
Handle empty inputs and boundary cases first.

Saturating 32-bit Multiply Without *

Return a*b using shift-and-add, saturating to INT_MAX or INT_MIN on overflow.

Constraints

Inputs are Python literals matching the function signature.
Return a deterministic exact-match value.

Examples

Input: (3, 5)

Expected Output: 15

Explanation: Positive values.

Input: (-7, 6)

Expected Output: -42

Explanation: Negative sign.

Input: (2147483647, 2)

Expected Output: 2147483647

Explanation: Positive overflow.

Input: (-2147483648, -1)

Expected Output: 2147483647

Explanation: INT_MIN times -1 saturates.

Hints

Choose a representation that makes the requested operation direct.
Handle empty inputs and boundary cases first.

Last updated: Jun 27, 2026

Loading coding console...