These problems are mixed on purpose and their titles do not name the pattern. Read the limits, decide the pattern, write the slow idea in your head, then code the one that fits. After each problem the explanation names the pattern you should have chosen.
0 /25 solved Easy 0/7 Medium 0/11 Hard 0/7
All Unsolved 25 Solved 0
Any level Easy Medium Hard
1. Pair that makes the target Easy 2. Reads the same both ways Easy 3. Sales between two days Easy 4. First ticket seen twice Easy 5. Find the delivery slot Easy 6. The odd one out Easy 7. Whole blocks only Easy 8. Best stretch of fixed length Medium 9. Fewest orders to reach the goal Medium 10. Stretches with an exact total Medium 11. Pairs within budget Medium 12. Longest run without a repeat Medium 13. Words with the same letters Medium 14. Smallest daily capacity Medium 15. Balanced brackets Medium 16. Search on a rotated shelf Medium 17. Subsets that hit the target Medium 18. Big powers with a remainder Medium 19. All valid bracket codes Hard 20. Ways to reach the top floor Hard 21. Longest run after a few repairs Hard 22. Shortest text that covers the letters Hard 23. Two lost codes Hard 24. Longest balanced stretch Hard 25. Three values that cancel out Hard 