AlgoSolveoRoadmap › Stage 7: Heaps & Backtracking › Pattern 35 of 53
DSA pattern guide
Backtracking — Sequence Gen
Generate all strings or structures from rules (phone letters, operators).
Use it when
Generate all strings or structures from rules (phone letters, operators).
Key idea
Build the sequence one position at a time over every allowed choice. Memoize when sub-results repeat.
Practice problems, in order
- Letter Combinations of a Phone NumberMedium
- All Possible Full Binary TreesMedium
- Expression Add OperatorsHard
- Word Break IIHard
How to practise this pattern
- Read the problem and look for the signal above before writing any code.
- Say the brute force out loud, with its time complexity, then ask what work it repeats.
- Apply the key idea and write the optimised version yourself.
- If you're stuck for more than 10 minutes, take one small hint, not the full solution.
- Move to the next problem only when you can explain why this pattern fits.
Stuck on one of these?
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