Week 2 Cold Revisit

This Friday, before any new work, re-solve two prior problems cold: no notes, no prior code open, no AI, the standard 25-minute struggle floor on each. The first solve taught the pattern; this blind re-solve is what makes it stick. This is the first cold revisit of the course, so it sets the habit you will repeat every Friday from here on.

The two problems

  1. Two Sum (Week 1, Arrays and Hashing). https://leetcode.com/problems/two-sum/
  2. Valid Anagram (Week 1, Arrays and Hashing). https://leetcode.com/problems/valid-anagram/

How to run the revisit

  • Do not look up which pattern either problem belongs to. Recognizing it cold, from the problem statement alone, is the entire point of the exercise; the tutor will not tell you.
  • Start each from a blank file. Name the pattern aloud, write the plain-English approach as a comment, then code.
  • Apply the 25-minute floor to each independently. If you stall past the floor, use the hint ladder, one rung per ask.
  • Submit each to LeetCode’s judge. The judge is the oracle, not the tutor.
  • Debrief each with the five questions in your commit message, and log the outcome in .tutor/revisit-log.md.

Neither problem is a two-pointer problem, and that is deliberate. The cold revisit trains recognition across the whole course, so the muscle you build is “read a cold statement and feel the pattern”, not “apply this week’s pattern again”. Two Sum is the sharper test of the two: this week you also solved Two Sum II, the same question on a sorted array, with two pointers in O(1) space. Coming back to the unsorted original should make you feel the cue flip back to a hash map, because the array is no longer sorted and the directional rule no longer applies. If either problem comes back slower than you expect, that is the signal for where to spend your next stretch session.