Intel Coding Interview Questions
25 Intel coding interview problems with full optimal solutions — 19 easy, 6 medium, 0 hard. Every problem ships with multiple approaches (brute-force first, then the optimal), complexity tables for each, company-specific tips on what an Intel interviewer values, and a FAQ section.
Showing 6 problems of 25
- #7mediumfrequently asked
7. Reverse Integer
Given a signed 32-bit integer x, return x with its digits reversed. If the reversed number overflows 32-bit range, return 0. Intel asks because the entire problem is an overflow-detection puzzle in disguise — the candidate who pre-checks for overflow before multiplying is the candidate who would catch the same bug in firmware.
3 free resourcesSolve → - #8mediumcompany favorite
8. String to Integer (atoi)
Implement atoi without using the language's parseInt. Intel loves this question because it's pure edge-case discipline — leading whitespace, optional sign, overflow clamping, non-digit termination. The rubric grades whether you handle every edge case before writing the happy-path loop.
3 free resourcesSolve → - #50mediumcompany favorite
50. Pow(x, n)
Implement pow(x, n) without using the language's exponent operator. Intel asks because the optimal O(log n) fast-exponentiation algorithm is the same algorithm that ships inside modular-exponentiation hardware for RSA acceleration — and the negative-exponent and INT_MIN edge cases trip ~40% of candidates.
3 free resourcesSolve → - #53mediumfrequently asked
53. Maximum Subarray
Given an integer array, find the contiguous subarray with the largest sum. Intel asks because Kadane's algorithm is the textbook DP entry point — the candidate who derives it from the invariant 'best ending here' before writing code is the candidate who can later derive less-famous DPs from first principles.
4 free resourcesSolve → - #204mediumfrequently asked
204. Count Primes
Count primes strictly less than n. Intel reaches for this in SWE-II rounds because the Sieve of Eratosthenes is a textbook cache-friendly algorithm — sequential memory access, branchless marking, perfect for SIMD. Naive trial-division candidates get filtered out fast.
3 free resourcesSolve → - #287mediumcompany favorite
287. Find the Duplicate Number
n+1 integers in [1, n] are placed in an array. Exactly one number is repeated. Find it WITHOUT modifying the array and using O(1) extra space. Intel loves this one because the only O(1)-space algorithm requires reframing array indices as a linked list and applying Floyd's cycle detection — a real 'aha' moment that separates senior IC from mid-level.
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