CircleCI Coding Interview Questions
27 CircleCI coding interview problems with full optimal solutions — 16 easy, 8 medium, 3 hard. Every problem ships with multiple approaches (brute-force first, then the optimal), complexity tables for each, company-specific tips on what an CircleCI interviewer values, and a FAQ section.
Showing 16 problems of 27
- #1easyfoundational
1. Two Sum
Given an array of integers and a target, return indices of the two numbers that add up to the target.
- #2easyfoundational
2. Valid Parentheses
Determine if a string of brackets is properly balanced and correctly nested.
- #3easyfoundational
3. Merge Two Sorted Lists
Splice two sorted linked lists into a single sorted list.
- #4easyfoundational
4. Remove Duplicates from Sorted Array
Remove duplicates in-place from a sorted array and return the new length.
- #5easyfoundational
5. Remove Element
Remove all occurrences of a target value from an array in-place.
- #6easyfoundational
6. Search Insert Position
Find the index where a target would be inserted in a sorted array to keep it sorted.
- #7easyfoundational
7. Maximum Subarray
Find the contiguous subarray with the largest sum.
- #8easyfoundational
8. Plus One
Increment a number represented as an array of digits by one.
- #9easyfoundational
9. Merge Sorted Array
Merge two sorted arrays in-place into the first one.
- #10easyfoundational
10. Binary Tree Inorder Traversal
Return the in-order traversal of a binary tree's node values.
- #11easyfoundational
11. Same Tree
Check whether two binary trees are structurally and value-wise identical.
- #12easyfoundational
12. Symmetric Tree
Determine whether a binary tree is a mirror of itself.
- #13easyfoundational
13. Maximum Depth of Binary Tree
Find the maximum depth of a binary tree, mirroring how CircleCI measures the critical path length of a pipeline DAG.
- #14easyfoundational
14. Path Sum
Determine if a binary tree has a root-to-leaf path summing to a target, analogous to checking if a CI pipeline path meets a cost budget.
- #15easyfoundational
15. Pascal's Triangle
Generate Pascal's triangle up to numRows, testing your ability to build iterative tabular structures common in test-result matrix generation at CircleCI.
- #16easyfoundational
16. Best Time to Buy and Sell Stock
Find the maximum profit from one stock transaction, testing the single-pass minimum-tracking pattern used in CI job cost optimization at CircleCI.