LeetCode Easy Problems 50¶

(a.k.a. The Illusion of Simplicity)

Welcome to LeetCode Easy — where problems look friendly… until you realize you’ve spent two hours debugging a typo in your “two-sum” function.

Think of this as Algorithm Kindergarten — it’s colorful, gentle, and still occasionally soul-crushing.

Problem	Concept	Comedy Summary
Two Sum	Hash Map	“Find two numbers that add up. Sounds easy. Until it’s not.”
Valid Parentheses	Stack	“The only time brackets matter more than emotions.”
Merge Two Sorted Lists	Linked List	“Basically Tinder for numbers — two lists find love.”
Maximum Subarray	Kadane’s Algorithm	“Find happiness in consecutive chaos.”
Reverse Linked List	Pointer manipulation	“A spiritual journey in reverse.”
Best Time to Buy and Sell Stock	Greedy algorithm	“Buy low, sell high — capitalism in Python form.”
Palindrome Number	Math	“Check if a number reads the same both ways. Like 121 or mom.”
Fibonacci Number	Recursion or DP	“Where everyone learns why recursion cries for help.”

Each “Easy” problem is a warm-up for harder algorithms. You’re not just coding — you’re training your brain to see patterns.

Pro Tip: When you can solve Two Sum in your sleep, you’re halfway to enlightenment. When you can do it without Googling, you’re a Jedi. 🧘‍♂️

“LeetCode Easy is like the tutorial level in a video game — but you still manage to die a few times.” 🎮

# Your code here

Exercises¶

Implement the classic two_sum(nums, target) that returns indices of the two numbers adding to target. Use a hash table for O(n) time.