Coding Interview
70. Climbing Stairs
Jason Yang · 04 Aug, 2026
Climbing Stairs (LeetCode 70): why the answer is Fibonacci, the memoized and bottom-up solutions in Java, and the rolling trick that drops it to O(1) space.
Blog posts — page 15
Coding Interview
Linked Lists: Rewiring Pointers Without Losing the List
Jason Yang · 04 Aug, 2026
Linked list problems in Java are three pointer moves: the dummy head, fast and slow pointers, and in-place reversal — plus the one that's a data structure.
Coding Interview
Graphs: Most of Them Don't Look Like Graphs
Jason Yang · 03 Aug, 2026
Most graph interview problems are disguised — grids, prerequisites, connectivity. How to spot them, the visited set trees never needed, and BFS vs DFS in Java.
Coding Interview
Binary Trees: Recursion and the Right Traversal
Jason Yang · 03 Aug, 2026
Binary tree problems in Java are recursion plus the right traversal: pre/in/post-order DFS vs BFS, what each recursive call returns, and the BST in-order trick.
Coding Interview
Arrays and Hashing: Trading Memory for a Faster Lookup
Jason Yang · 03 Aug, 2026
Arrays and hashing in Java: how a hash set or map trades memory for O(1) lookups to turn O(n^2) scans linear, and when hashing is the wrong reflex.