tianyefan/grokking_to_leetcode.md

GROKKING NOTES

I liked the way Grokking the coding interview organized problems into learnable patterns. However, the course is expensive and the majority of the time the problems are copy-pasted from leetcode. As the explanations on leetcode are usually just as good, the course really boils down to being a glorified curated list of leetcode problems.

So below I made a list of leetcode problems that are as close to grokking problems as possible.

1. Pattern: Sliding Window

• https://leetcode.com/problems/maximum-subarray/ # Close enough
• https://leetcode.com/problems/minimum-size-subarray-sum/
• https://leetcode.com/problems/longest-substring-with-at-most-k-distinct-characters/
• https://leetcode.com/problems/fruit-into-baskets/
• https://leetcode.com/problems/longest-substring-without-repeating-characters/
• https://leetcode.com/problems/longest-repeating-character-replacement/
• https://leetcode.com/problems/max-consecutive-ones-iii/
• https://leetcode.com/problems/permutation-in-string/
• https://leetcode.com/problems/find-all-anagrams-in-a-string/
• https://leetcode.com/problems/minimum-window-substring/
• https://leetcode.com/problems/substring-with-concatenation-of-all-words/

2. Pattern: Two Pointers

• https://leetcode.com/problems/two-sum/
• https://leetcode.com/problems/remove-duplicates-from-sorted-array/
• https://leetcode.com/problems/squares-of-a-sorted-array/
• https://leetcode.com/problems/3sum/
• https://leetcode.com/problems/3sum-closest/
• https://leetcode.com/problems/3sum-smaller/
• https://leetcode.com/problems/subarray-product-less-than-k/
• https://leetcode.com/problems/sort-colors/
• https://leetcode.com/problems/4sum/
• https://leetcode.com/problems/backspace-string-compare/
• https://leetcode.com/problems/shortest-unsorted-continuous-subarray/

3. Pattern: Fast & Slow pointers

• https://leetcode.com/problems/linked-list-cycle/
• https://leetcode.com/problems/linked-list-cycle-ii/
• https://leetcode.com/problems/happy-number/
• https://leetcode.com/problems/middle-of-the-linked-list/
• https://leetcode.com/problems/palindrome-linked-list/
• https://leetcode.com/problems/reorder-list/
• https://leetcode.com/problems/circular-array-loop/

4. Pattern: Merge Intervals

• https://leetcode.com/problems/merge-intervals/
• https://leetcode.com/problems/insert-interval/
• https://leetcode.com/problems/interval-list-intersections/
• https://leetcode.com/problems/meeting-rooms-ii/
• Could not find equivalent. Given a list of intervals with values, find the peak sum (i.e. if intervals are overlapping, sum their values)
• https://leetcode.com/problems/employee-free-time/

5. Pattern: Cyclic Sort

• Couldn't find equivalent for the first question. The second question below encompasses the first one though. See https://leetcode.com/problems/missing-number/discuss/859510/C%2B%2B-O(N)-O(1)-using-Cyclic-Sort for how grokking the coding interview approached these problems. It uses the fact that we can sort the array in O(n) without comparison operators
• https://leetcode.com/problems/missing-number/
• https://leetcode.com/problems/find-all-numbers-disappeared-in-an-array/
• https://leetcode.com/problems/find-all-duplicates-in-an-array/
• combine https://leetcode.com/problems/find-the-duplicate-number/ and https://leetcode.com/problems/missing-number/
• https://leetcode.com/problems/first-missing-positive/
• https://leetcode.com/problems/kth-missing-positive-number/

6. Pattern: In-place Reversal of a LinkedList

• https://leetcode.com/problems/reverse-linked-list/
• https://leetcode.com/problems/reverse-linked-list-ii/
• https://leetcode.com/problems/reverse-nodes-in-k-group/
• Next question is the same, but alternate each subgroup
• https://leetcode.com/problems/rotate-list/

7. Pattern: Tree Breadth First Search

• https://leetcode.com/problems/binary-tree-level-order-traversal/
• https://leetcode.com/problems/binary-tree-level-order-traversal-ii/
• https://leetcode.com/problems/binary-tree-zigzag-level-order-traversal/
• https://leetcode.com/problems/minimum-depth-of-binary-tree/
• https://leetcode.com/problems/inorder-successor-in-bst/ # Close, not exact
• https://leetcode.com/problems/populating-next-right-pointers-in-each-node/ # Close, grokk assumes non-perfect tree
• Next question is the same, but connect end nodes to the next level instead of null
• https://leetcode.com/problems/binary-tree-right-side-view/

8. Pattern: Tree Depth First Search
9. Pattern: Two Heaps
10. Pattern: Subsets
11. Pattern: Modified Binary Search
12. Pattern: Bitwise XOR
13. Pattern: Top 'K' elements
14. Pattern: K-way merge
15. Pattern: 0/1 Knapsack
16. Pattern: Topological Sort

https://leetcode.com/problems/kth-largest-element-in-an-array/