Microsoft Coding Interview Questions
20 Microsoft coding interview problems with full optimal solutions — 5 easy, 13 medium, 2 hard. Every problem ships with multiple approaches (brute-force first, then the optimal), complexity tables for each, company-specific tips on what an Microsoft interviewer values, and a FAQ section.
Showing 5 problems of 20
- #20easyfoundational
20. Valid Parentheses
Valid Parentheses is the Microsoft warm-up that tests whether you can pick the right data structure on the first try. The answer is always a stack — explain why before writing code, and use a closing-to-opening hash map so the matching logic is a single comparison.
4 free resourcesSolve → - #168easyfrequently asked
168. Excel Sheet Column Title
Excel Sheet Column Title is Microsoft's deliberately-off-by-one base-26 puzzle. Excel columns A..Z, AA..AZ, BA.. are 1-indexed with no zero digit, so a vanilla base-26 conversion is wrong. The fix is subtracting one before every modulo.
4 free resourcesSolve → - #202easyfrequently asked
202. Happy Number
Happy Number is Microsoft's favorite cycle-detection question disguised as math. The trick is recognizing the digit-square sum sequence either reaches 1 or enters a cycle — so Floyd's tortoise-and-hare applies and the space drops to O(1).
4 free resourcesSolve → - #206easyfoundational
206. Reverse Linked List
Reverse Linked List is Microsoft's go-to pointer-manipulation warm-up. Interviewers want you to talk through the three-pointer dance (prev, curr, next) without losing the rest of the list and to mention the recursive variant before they ask.
4 free resourcesSolve → - #703easyfrequently asked
703. Kth Largest Element in a Stream
Kth Largest Element in a Stream is Microsoft's go-to question for whether you reach for the right data structure when 'streaming' enters the problem. The answer is a min-heap of size k — anything else (sorted list, max-heap) has the wrong asymptotic cost.
4 free resourcesSolve →
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