Day56
60-day SSE plan
Cache (LRU) • Uber-style Ride Hailing • Two Pointers • Tech: Docker
Algorithm
DSA
Two Pointers — Trapping Rain Water (LC 42)
Compute trapped water using two-pointer approach.
Example
Input: [0,1,0,2,1,0,1,3,2,1,2,1] → Output: 6
Where it shows up
Resource aggregation, elevation maps, histogram problems.
References
Low-level design
LLD
Cache (LRU)
Requirements
- Put/get with capacity; LRU eviction policy.
Expectations
- Classes for LRUCache using LinkedHashMap or custom DLL+HashMap.
- Complexity guarantees O(1) operations.
Where it shows up
Databases, OS page cache, web caching layers.
References
High-level design
HLD
Uber-style Ride Hailing
Requirements
- Driver/rider match by proximity; live location; trip lifecycle; pricing.
Expectations
- Geo-indexing (geohash), matching service, WS gateway, storage model.
- Regional partitions, degradation strategies.
Where it shows up
Mobility platforms, logistics dispatch.
References
Today's deep-dive
Tech
Docker
Create multi-stage build for a Spring Boot app; add HEALTHCHECK; test graceful shutdown.
Where it shows up
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References