Data Structures & Algorithms
21 pieces. Two tracks.Zero filler.
Hand-written explanations of the patterns, problems and designs that show up in real interviews — and real engineering. Each piece leads with the insight, then the code.
SSE 60-Day Interview Plan
A daily prep plan for Senior Software Engineer loops. Each day pairs one DSA pattern with an LLD problem, an HLD problem and a rotating tech focus — Java, Kafka, Cassandra, Spring Boot, Kubernetes and more.
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Problems
Two Sum
Find two indices whose values sum to a target. The classic O(n) hashmap warm-up.
Problems
Longest Substring Without Repeating Characters
Sliding window with a 'last seen' index — O(n), single pass.
Problems
Container With Most Water
Maximize trapped area between two vertical lines — two pointers from each end.
Patterns
Sliding Window
Two pointers that move in the same direction to compute window-based answers in O(n).
Patterns
Two Pointers
Two indices moving from opposite ends — turns sorted-array search problems into O(n).
Patterns
Fast & Slow Pointers (Floyd's)
One pointer moves twice as fast as the other — used to detect cycles and find midpoints in linked lists.