14. Revision Days — Checkpoints

Every 15 days, pause and revisit previously solved problems. Spaced repetition ensures long-term retention.

Checkpoint	Day	Topics to Revise	Suggested Problems
R1	14	Arrays, Strings	Two Sum, Valid Palindrome, Valid Anagram, Reverse String
R2	29	Linked Lists, Stacks & Queues	Reverse Linked List, Merge Two Lists, Valid Parentheses, Min Stack
R3	44	Trees, BST	Max Depth, Symmetric Tree, LCA, Inorder traversal
R4	59	Binary Search	Search Insert Position, Peak Element, Rotated Array
R5	74	Graphs	Number of Islands, Clone Graph, Course Schedule
R6	89	Dynamic Programming	Climbing Stairs, Coin Change, House Robber, LIS
R7	104	Greedy	Gas Station, Trapping Rain Water, Partition Labels
R8	119	Backtracking	Permutations, Generate Parentheses, N-Queens
R9	134	All DSA topics	Pick 5 hard problems across topics
R10	135	All DSA topics + SD	Timed mock — 3 problems in 90 min

Revision Strategy

Re-solve each problem from scratch (no peeking at solution)
Compare your approach with the optimal solution
If you can't solve in 15 min, review the pattern and try again tomorrow
Track accuracy in a spreadsheet — target >80% on revision day

✏️ Exercise: On your next revision day, re-solve Two Sum, Reverse Linked List, Max Depth, Number of Islands, and Climbing Stairs without looking at solutions. Time yourself.