Problems

Easy

• Binary tree diameter

• Search in a binary search tree

• 1-bit and 2-bit characters

• Climbing stairs

• Flipping an image

• Hamming distance

• Happy number

• Jewels and stones

• Judge route circle

• Lemonade change

• Merge two binary trees

• Movies on flight

• Peak index in a mountain array

• Permutation

• Ransom note

• Same tree

• String compression

• Two sum

• Unique Morse code words

• Unique string

• Valid parentheses

Medium

• Add two numbers

• All paths from source to target

• Binary tree pruning

• 01 matrix

• 2-key keyboard

• Encode and decode TinyURL

• Is subsequence?

• Kth smallest element in a sorted matrix

• Longest substring without repeating characters

• Max increase to keep city skyline

• Maximal square

• Maximum Binary Tree

• Network delay time

• One-edit distance

• Reach a number

• Remove nth node from end of list

• Triangle

• Zero matrix

Hard

• Find minimum in rotated sorted array
• Jump game
• Range module
• Sliding window maximum
• Word ladder