Interview Prep

DSA Problem List

105 problems: all 75 from the default Grind 75 list plus 30 extras that fill pattern gaps (monotonic stack, union-find, Dijkstra, LIS/LCS/edit distance, greedy) and Week 3 mixed practice.

Track progress in the tracker (status, time, notes and redo dates). Easy problems are warm-ups at 5.5 YOE: if the solution is obvious, code it fast or skip it. Status, time and mistake notes live in tracker/interview_prep_tracker.xlsx.

LeetCode links were built from problem slugs from memory; fix any that 404.

Week 1

Day 1 — Wed 21 Oct · Arrays & hashing, two pointers

Done # Problem Difficulty Pattern Source
☐ 1 Two Sum Easy Arrays & hashing Grind 75
☐ 2 Valid Anagram Easy Arrays & hashing Grind 75
☐ 3 Contains Duplicate Easy Arrays & hashing Grind 75
☐ 4 Valid Palindrome Easy Two pointers Grind 75
☐ 5 Product of Array Except Self Medium Arrays & hashing Grind 75
☐ 6 3Sum Medium Two pointers Grind 75
☐ 7 Container With Most Water Medium Two pointers Grind 75
☐ 8 Sort Colors Medium Two pointers Grind 75

Day 2 — Thu 22 Oct · Sliding window

Done # Problem Difficulty Pattern Source
☐ 9 Best Time to Buy and Sell Stock Easy Sliding window Grind 75
☐ 10 Maximum Subarray Medium Sliding window Grind 75
☐ 11 Longest Substring Without Repeating Characters Medium Sliding window Grind 75
☐ 12 Find All Anagrams in a String Medium Sliding window Grind 75
☐ 13 Minimum Window Substring Hard Sliding window Grind 75

Day 3 — Fri 23 Oct · Binary search (incl. on the answer)

Done # Problem Difficulty Pattern Source
☐ 14 Binary Search Easy Binary search Grind 75
☐ 15 First Bad Version Easy Binary search Grind 75
☐ 16 Search in Rotated Sorted Array Medium Binary search Grind 75
☐ 17 Time Based Key-Value Store Medium Binary search Grind 75
☐ 18 Koko Eating Bananas Medium Binary search Extra

Day 4 — Sat 24 Oct · Stacks, monotonic stacks & heaps

Done # Problem Difficulty Pattern Source
☐ 19 Valid Parentheses Easy Stack Grind 75
☐ 20 Implement Queue using Stacks Easy Stack Grind 75
☐ 21 Min Stack Medium Stack Grind 75
☐ 22 Evaluate Reverse Polish Notation Medium Stack Grind 75
☐ 23 Daily Temperatures Medium Stack Extra
☐ 24 Largest Rectangle in Histogram Hard Stack Grind 75
☐ 25 K Closest Points to Origin Medium Heap Grind 75
☐ 26 Top K Frequent Elements Medium Heap Extra
☐ 27 Task Scheduler Medium Heap Grind 75
☐ 28 Merge k Sorted Lists Hard Heap Grind 75
☐ 29 Find Median from Data Stream Hard Heap Grind 75

Day 5 — Sun 25 Oct · Linked lists & trees

Done # Problem Difficulty Pattern Source
☐ 30 Merge Two Sorted Lists Easy Linked list Grind 75
☐ 31 Linked List Cycle Easy Linked list Grind 75
☐ 32 Reverse Linked List Easy Linked list Grind 75
☐ 33 Middle of the Linked List Easy Linked list Grind 75
☐ 34 Invert Binary Tree Easy Tree Grind 75
☐ 35 Maximum Depth of Binary Tree Easy Tree Grind 75
☐ 36 Balanced Binary Tree Easy Tree Grind 75
☐ 37 Diameter of Binary Tree Easy Tree Grind 75
☐ 38 Lowest Common Ancestor of a BST Medium Tree Grind 75
☐ 39 Binary Tree Level Order Traversal Medium Tree Grind 75
☐ 40 Validate Binary Search Tree Medium Tree Grind 75
☐ 41 Kth Smallest Element in a BST Medium Tree Grind 75
☐ 42 Lowest Common Ancestor of a Binary Tree Medium Tree Grind 75
☐ 43 Binary Tree Right Side View Medium Tree Grind 75

Day 6 — Mon 26 Oct · Timed mock: mixed set

Done # Problem Difficulty Pattern Source
☐ 44 Spiral Matrix Medium Matrix Grind 75
☐ 45 String to Integer (atoi) Medium String Grind 75
☐ 46 Add Binary Easy String Grind 75
☐ 47 LRU Cache Medium Design Grind 75

Day 7 — Tue 27 Oct · Review misses + leftover easies

Done # Problem Difficulty Pattern Source
☐ 48 Ransom Note Easy Arrays & hashing Grind 75
☐ 49 Majority Element Easy Arrays & hashing Grind 75
☐ 50 Longest Palindrome Easy Arrays & hashing Grind 75

Week 2

Day 8 — Wed 28 Oct · Graphs: BFS/DFS, topological sort

Done # Problem Difficulty Pattern Source
☐ 51 Flood Fill Easy Graph Grind 75
☐ 52 Number of Islands Medium Graph Grind 75
☐ 53 Rotting Oranges Medium Graph Grind 75
☐ 54 01 Matrix Medium Graph Grind 75
☐ 55 Clone Graph Medium Graph Grind 75
☐ 56 Course Schedule Medium Graph Grind 75

Day 9 — Thu 29 Oct · Graphs: union-find, Dijkstra

Done # Problem Difficulty Pattern Source
☐ 57 Accounts Merge Medium Union-find Grind 75
☐ 58 Redundant Connection Medium Union-find Extra
☐ 59 Network Delay Time Medium Dijkstra Extra
☐ 60 Minimum Height Trees Medium Graph Grind 75
☐ 61 Word Ladder Hard Graph Grind 75

Day 10 — Fri 30 Oct · DP: 1D & 2D grid

Done # Problem Difficulty Pattern Source
☐ 62 Climbing Stairs Easy DP Grind 75
☐ 63 House Robber Medium DP Extra
☐ 64 Coin Change Medium DP Grind 75
☐ 65 Unique Paths Medium DP Grind 75

Day 11 — Sat 31 Oct · DP: knapsack, LIS, strings

Done # Problem Difficulty Pattern Source
☐ 66 Partition Equal Subset Sum Medium DP Grind 75
☐ 67 Longest Increasing Subsequence Medium DP Extra
☐ 68 Word Break Medium DP Grind 75
☐ 69 Longest Palindromic Substring Medium DP Grind 75
☐ 70 Longest Common Subsequence Medium DP Extra
☐ 71 Edit Distance Medium DP Extra
☐ 72 Maximum Profit in Job Scheduling Hard DP Grind 75

Day 12 — Sun 01 Nov · Backtracking, tries, intervals, greedy

Done # Problem Difficulty Pattern Source
☐ 73 Subsets Medium Backtracking Grind 75
☐ 74 Permutations Medium Backtracking Grind 75
☐ 75 Combination Sum Medium Backtracking Grind 75
☐ 76 Letter Combinations of a Phone Number Medium Backtracking Grind 75
☐ 77 Word Search Medium Backtracking Grind 75
☐ 78 Implement Trie (Prefix Tree) Medium Trie Grind 75
☐ 79 Insert Interval Medium Intervals Grind 75
☐ 80 Merge Intervals Medium Intervals Grind 75
☐ 81 Jump Game Medium Greedy Extra

Day 13 — Mon 02 Nov · Timed mock: mixed set

Done # Problem Difficulty Pattern Source
☐ 82 Construct Binary Tree from Preorder and Inorder Traversal Medium Tree Grind 75
☐ 83 Kth Largest Element in an Array Medium Heap Extra
☐ 84 Trapping Rain Water Hard Two pointers Grind 75
☐ 85 Serialize and Deserialize Binary Tree Hard Tree Grind 75

Day 14 — Tue 03 Nov · Mixed practice

Done # Problem Difficulty Pattern Source
☐ 86 Basic Calculator Hard Stack Grind 75
☐ 87 Group Anagrams Medium Arrays & hashing Extra
☐ 88 Longest Consecutive Sequence Medium Arrays & hashing Extra

Week 3

Day 15 — Wed 04 Nov · Mixed practice

Done # Problem Difficulty Pattern Source
☐ 89 Sliding Window Maximum Hard Sliding window Extra
☐ 90 Decode Ways Medium DP Extra
☐ 91 Pacific Atlantic Water Flow Medium Graph Extra

Day 16 — Thu 05 Nov · Mixed practice

Done # Problem Difficulty Pattern Source
☐ 92 Gas Station Medium Greedy Extra
☐ 93 Maximal Square Medium DP Extra
☐ 94 Course Schedule II Medium Graph Extra

Day 17 — Fri 06 Nov · Mixed practice

Done # Problem Difficulty Pattern Source
☐ 95 Find Minimum in Rotated Sorted Array Medium Binary search Extra
☐ 96 Non-overlapping Intervals Medium Intervals Extra
☐ 97 House Robber II Medium DP Extra

Day 18 — Sat 07 Nov · Mixed timed practice

Done # Problem Difficulty Pattern Source
☐ 98 Rotate Image Medium Matrix Extra
☐ 99 Set Matrix Zeroes Medium Matrix Extra
☐ 100 Remove Nth Node From End of List Medium Linked list Extra
☐ 101 Word Search II Hard Trie Extra

Day 19 — Sun 08 Nov · Mixed timed practice

Done # Problem Difficulty Pattern Source
☐ 102 Reorder List Medium Linked list Extra
☐ 103 Copy List with Random Pointer Medium Linked list Extra
☐ 104 Path Sum III Medium Tree Extra
☐ 105 Binary Tree Maximum Path Sum Hard Tree Extra