Cisco Coding Interview Questions
30 Cisco coding interview problems with full optimal solutions — 6 easy, 22 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 Cisco interviewer values, and a FAQ section.
Showing 6 problems of 30
- #20easyfoundational
20. Valid Parentheses
Valid Parentheses at Cisco is a 5-minute warm-up where the interviewer just wants to confirm you know what a stack is. Skip it in under 10 minutes and you've earned the harder graph round. The interviewer is grading whether you map closing brackets to openers correctly and whether you handle the empty-stack pop.
2 free resourcesSolve → - #70easyfoundational
70. Climbing Stairs
Climbing Stairs at Cisco is a 5-minute DP warm-up that filters for candidates who recognize the Fibonacci recurrence. The interviewer wants the O(1)-space bottom-up loop and is grading whether you go straight there or get stuck in naive recursion.
3 free resourcesSolve → - #121easyfoundational
121. Best Time to Buy and Sell Stock
Best Time to Buy and Sell Stock at Cisco is a one-pass scan that masquerades as DP. The interviewer is checking whether you maintain a 'minimum-so-far' invariant and compute profit against it at every position, all in one walk.
2 free resourcesSolve → - #141easyfoundational
141. Linked List Cycle
Linked List Cycle at Cisco is the second-most common pointer warm-up after Reverse Linked List. The interviewer wants Floyd's tortoise-and-hare so you can detect the loop in O(1) extra space. The hash-set version is the fallback when you can't articulate why two pointers eventually meet.
3 free resourcesSolve → - #206easyfoundational
206. Reverse Linked List
Reverse Linked List at Cisco is a 10-minute warm-up to filter for candidates who can implement pointer manipulation without losing track of the next-pointer save. The interviewer wants the iterative three-pointer pattern, and they pivot to recursive as a follow-up.
3 free resourcesSolve → - #997easyfrequently asked
997. Find the Town Judge
Find the Town Judge at Cisco is a graph in-degree / out-degree problem disguised as a trust puzzle. The interviewer is checking whether you can recast 'judge = everyone trusts them, they trust no one' as 'in-degree N-1, out-degree 0' on a directed graph.
2 free resourcesSolve →
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