DSA Factory
Curriculum
Level 1 · Foundations

Strings

About 24 steps, from the first idea to a mastery test.

  1. Stage 0Walking a stringFree
    1. 1A string is a row of characters6 min
    2. 2Building a new string7 min
    3. 3Compare from both ends7 min
    4. 4Letters are numbers9 min
  2. Stage 1Counting charactersFree
    1. 1Twenty-six boxes7 min
    2. 2Same letters, any order7 min
    3. 3Count first, then look7 min
    4. 4Enough letters?7 min
  3. Stage 2Two pointers on textFree
    1. 1Find a word's two ends9 min
    2. 2One mismatch allowed10 min
    3. 3Measure each run8 min
    4. 4Two strings, two pointers6 min
  4. Stage 3Windows on textFree
    1. 1Jump past the repeat10 min
    2. 2Slide the letter counts10 min
    3. 3At most k kinds10 min
    4. 4Cover everything, then tighten14 min
  5. Stage 4ParsingFree
    1. 1Reading a number from text10 min
    2. 2Cut at every separator8 min
    3. 3Column by column8 min
    4. 4Compare piece by piece10 min
  6. Stage 5MasteryFree
    1. 1Build a palindrome10 min
    2. 2Made of copies?10 min
    3. 3Longest mirror inside14 min
    4. 4Exactly k kinds14 min
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