DSA - 2 new, 1 revision (Greedy, Kadane, Linked List)

New Problems

435. Non-overlapping Intervals

• Concept: Greedy
• Insight:
  Sort intervals based on start. Iterate and compare adjacent intervals while maintaining prevEnd.
  • If no overlap → update prevEnd
  • If overlap → increment count and update prevEnd = min(prevEnd, currEnd)
• Comment:
  Solved partial conditions independently. Needed a hint to unlock the core greedy idea, then implemented successfully.

53. Maximum Subarray

• Concept: Kadane’s Algorithm
• Insight:
  At each step, track max of:
  • current element
  • sum till now + current
    Maintain a global maximum.
• Comment:
  Recognized the pattern after hint. Execution was straightforward once direction was clear.

Revision

23. Merge K Sorted Lists

• Concept: Linked List, Divide & Conquer (Iterative merge)
• Approach:
  Repeatedly merge 2 sorted lists and pass the result forward.
• Comment:
  Reinforced the idea that breaking K into pairs simplifies complexity mentally and implementation-wise.

🧘 Reflection

The optimal LeetCode strategy is becoming clearer:

• Phase 1:
  2 new problems/day for ~10–12 days → build exposure

• Phase 2:
  1 new + multiple revisions → solidify patterns

True ROI doesn’t come from solving new problems alone —
it comes from revisiting and internalizing patterns through spaced repetition.

LeetCode mastery is less about intelligence, more about memory + pattern recall under pressure.

At least for mid-level grinders — this is the game.