tagging every leetcode problem with #LeetCode

• also making their names include leetcode and it’s number

implementations of basic data structures

(../..Readme) path is diff for nested folders this needs to be fixed appropriately.

do problem notes on the intervals pattern Intervals & Ranges Pattern (Sorting)

• Problems

  Here’s the tight top-10, ordered by priority and picked for FAANG frequency + coverage breadth (not difficulty):

  1. Merge Intervals (LC 56) — the pattern itself. Asked everywhere (Google, Meta, Amazon). If you only do one, this is it.
  2. Insert Interval (LC 57) — Google favorite. Tests real understanding vs memorized loop.
  3. Meeting Rooms II (LC 253) — Amazon/Meta staple. First heap-based sweep, very common as a “design a scheduler” follow-up too.
  4. Non-overlapping Intervals (LC 435) — the greedy/sort-by-end fork. Amazon, Bloomberg regulars. (MUST DO)
  5. Minimum Arrows to Burst Balloons (LC 452) — same idea as #4 restated, high frequency at Amazon/Google, good to confirm you generalize the pattern not memorize the problem. (must do)
  6. Interval List Intersections (LC 986) — two-pointer variant, Facebook/Meta favorite, cheap win once merge is solid.
  7. Meeting Rooms (LC 252) — quick, but shows up as a warm-up/phone-screen filter before II.
  8. Car Pooling (LC 1094) — diff array tool, Uber/Amazon-flavored, distinct technique from heap/merge so it rounds out coverage.
  9. My Calendar I (LC 729) — the online/incremental variant, tests if you can adapt without full upfront sort — shows up at Google/Meta.
  10. Employee Free Time (LC 759) — the “boss fight,” Google/LinkedIn hard-tier, combines flatten + merge + gap-find. Do this last to confirm mastery.

  Grouped by underlying technique — this is the map to hold in your head walking into an interview:

  1. Merge Sweep (sort by start → linear combine)

  • Merge Intervals (56)
  • Insert Interval (57)

  2. Two-Pointer Intersection (pre-sorted inputs, no merge needed)

  • Interval List Intersections (986)

  3. Greedy Selection (sort by end → keep smallest-end on conflict)

  • Non-overlapping Intervals (435)
  • Minimum Arrows to Burst Balloons (452)

  4. Sweep Line / Active-Count (sort by start → track concurrency via heap or two-pointer)

  • Meeting Rooms (252) — boolean check, no heap needed
  • Meeting Rooms II (253) — heap-based count

  5. Online/Incremental Sweep (no upfront sort possible — one insert at a time)

  • My Calendar I (729)

  6. Delta / Diff Array (range-add-then-query, distinct tool from heap)

  • Car Pooling (1094)

  7. Composite (chains multiple methods above in one problem)

  • Employee Free Time (759) — flatten + merge sweep + gap-finding

  Category 1 and 4 both sort by start but diverge on what they track (merged range vs concurrent count) — that’s the pair most people conflate. Category 3 is the one place the sort key flips to end, which is the fork worth drilling until it’s automatic.

Two heap approach

Strings variations and questions to do - string variations and patterns

• Some of the anagrams, rotations, etc. already done.
• have to learn trie to attempt a particular pattern
• lc 386 to do after dfs
• 336 - palindrome pairs (hard but popular)

linked list questions to put here

leetcode 556 is a variation of next-permutation-(leetcode-31) and nothing to do with monotonic stack. Do it also

Stack - stack patterns and variations (to do)

• leetcode 224 (basic calculator) solving infix strings - do it

Queue - Queue patterns and Variations

To do but not queue patterns (some bfs or combinatorial pattern) - BFS-Backtracking based Queue but not queue patterns

generate parenthesis - leetcode 22

leetcode - 17

leetcode - jump game VI, leetcode 1438 (deque, queue)

trie variations

• implement trie leetcode and others

Disjoint set union variations

Deque patterns variations

backtracking

• combination sum and all patterns - looks important
• overlaps a lot with dfs, DP and some problems are already done.

Greedy patterns

see huffman coding indirectly inspired problems - Huffman Coding (indirectly inspired)

see as well - Scheduling - Greedy - DP - Heap cluster