Leetcode

2022

I didn't record any information about the problems I've done. It would be ideal to classify problems and note how they were solved.

2023

Hash Table

• Two Sum: Check Hashmap for complement

Array

• Remove Duplicates: Swap placeholder for greater value
  • Plan before execution
• Remove Element: Swap placeholder for non-target
  • More or less, both remove problems just involve keeping track of two indices
• Plus One: Iterate backwards, unshift, and either logic or mod/divide.
• Merge: Using an array to hold values in sorted order until they're ready to be inserted
  • A better solution is to iterate backwards, placing the largest values in nums1.
• Pascal's Triangle: Just code the generation logic.
• Pascal's Triangle II: N/A
• Best Time to Buy and Sell Stock: Compare current lowest price with future prices until new lowest price is found, keeping track of highest profit.

String

• Roman to Integer: Utilize a hashmap, and add or subtract value depending on next symbol

Linked List

• Add Two Numbers: Div, mod, and carries
  • The cleanup for this one is really nice since no value can be changed to 0
• Merge Two Sorted Lists: Linked List understanding/knowledge.

Binary Search

• Search Insert: Just binary search, but return low if not found

Binary Search Tree

• Sorted Array to BST: Recursive solution that ensures every tree is a BST

Bitwise Operations

• Single Number: Xor

Dynamic Programming

• Climbing Stairs: Think of a decision tree + cache or think about fibo (how the previous two results create the next)