Check text intervals, score bounds, rank models, and ancestor tours

Choose the invariant or failure response implied by each operation contract. Verify the working program against a direct reference model.

Lessons

• FM-index backward search: narrow a suffix interval by character
• Block-max postings: skip safe document-score regions
• Piecewise interpolation indexes: predict a bounded rank window
• Euler-tour RMQ: answer static common ancestors in constant query time

Design exercise

• Project: audit text intervals, score bounds, rank models, and ancestor tours
• Data Structures