02-2026

Feb-28

• Review
  • 0217.Contains Duplicate - Easy
  • 0242.Valid Anagram - Easy
  • 0001.Two Sum - Easy
  • 0049.Group Anagrams - Medium
  • 0347.Top K Frequent Elements - Medium
  • 0271.Encode and Decode Strings - Medium

Feb-22

• Review
  • 0543.Diameter of Binary Tree - Solved, while left <= right
  • 0042.Trapping Rain Water - Hinted
  • 0022.Generate Parentheses - Solved, Time complexity O($2^{2n}$)
  • 0283.Move Zeroes - Hinted
  • 0696.Count Binary Substrings - Peeked
  • 0735.Asteroid Collision - Hinted, while alive and stack

Feb-21

• Review
  • 0146.LRU Cache - Hinted w bug, dll need self.key, call method add self._remove
  • 0128.Longest Consecutive Sequence - Hinted, iterate set
  • 0056.Merge Intervals - Solved, key = lambda x:x[0]
  • 0011.Container w Most Water - Solved
  • 0069.Sqrt(x) - edge case

Feb-20

• Review
  • 0015.3Sum - Solved w bug
• Redo
  • 0049.Group Anagrams - Solved
  • 0003.Longest Substring wo Repeating Characters - Solved, i = right(include) - left + 1

Feb-19

• Review
  • 0054.Spiral Matrix - Peeked
  • 0062.Unique Paths - Peeked

Feb-18

• Review
  • 0994.Rotting Oranges - Solved (take time debug)
  • 0046.Permutations - Solved (better use index)
  • 2965.Find Missing and Repeated Values - Solved
  • 0680.Valid Palindrome II - Peaked (approach)
  • 3010.Divide an Arr Into Sub With MiniCost I - Peeked (approach)
  • 0069.Sqrt(x) - Peeked (do not know approach)
  • 0258.Add Digits - Peeked
• Redo
  • 3010.Divide an Arr Into Sub With MiniCost I
  • 0069.Sqrt(x)
  • 0258.Add Digits

Feb-17

• Review
  • 0496.Next Greater Element I - better review again
• Done
  • 0110.Balanced Binary Tree - Hinted
  • 0845.Longest Mountain in Array - Hinted
• Redo
  • 0845.Longest Mountain in Array

Feb-16

• Review
  • 0240.Search a 2D Matrix II - Solved
    • time complexity
    • boundaries
• Done
  • 1480.Running Sum of 1d Array - Solved
  • 0096.Unique Binary Search Trees - Peeked
    • no idea
  • 0138.Copy List with Random Pointer - Solved
    • has better write
  • 0496.Next Greater Element I - Peeked
• Redo:
  • 0496.Next Greater Element I

Feb-15

• Done:
  • 0133.Clone Graph - Peeked
    • if nei not in hashmap, create its clone and pushnei
    • always connect
    • No visited needed
  • 0075.Sort Colors - Peeked
    • wrong approach
  • 0169.Majority Element - Peeked
    • don’t know method2
  • 0070.Climbing Stairs - Peeked
  • 0240.Search a 2D Matrix II - Peeked
    • wrong approach
• Redo
  • 0240.Search a 2D Matrix II

Feb-11

• Done:
  • 0199.Binary Tree Right Side View - Solved
  • 0560.Subarray Sum Equals K - Peeked
    • use wrong algorithm
  • 0739.Daily Temperatures - Peeked
• Redo:
  • redo: 0560.Subarray Sum Equals K

Feb-08

• 0098.Validate Binary Search Tree Peeked
  • redo: 0098.Validate Binary Search Tree

Feb-07

• 0007.Reverse Integer Peeked
  • Integers don’t have a .reverse() method (only lists do).
  • Math way to reverse an integer
• 3752.Lexicographically Smallest Peeked No idea

Feb-06

• 0003.Longest Substring wo Repeating Characters Solved
• 0169.Majority Element Solved w/o bug