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Prefix Constraints Ladder

Who This Is For

Use this ladder when a problem asks you to choose an optimal subset or ordering while every prefix must satisfy a capacity or balance rule.

Warm-Up

  • threshold-feasibility ordering
  • suffix-difference sanity checks

Core

  • greedy with heap support
  • exchange-argument style correctness

Example Notes

Exit Criteria

You are ready to move on when you can:

  • express the prefix constraint clearly
  • justify why the chosen greedy structure remains feasible at every step
  • use a heap or ordered structure to repair choices efficiently
  • distinguish this pattern from a full DP over prefixes

External Practice