LeetCode Challenge Day 4 — 3484. Design Spreadsheet

Hey folks

This is Day 4 of my LeetCode streak. Today’s problem is 3484. Design Spreadsheet — a parsing + state-management problem where you must support setting and resetting cells and evaluating simple =X+Y formulas where X and Y may be either integers or cell references like A1.

Below I restate the problem, describe a clean, robust approach, give a step-by-step solution and the full JavaScript implementation I used, analyze time & space complexity, list edge-cases and testing ideas, and finally embed a responsive (mobile-friendly) video walkthrough.

📌 Problem Statement

We are asked to implement a Spreadsheet class with the following features:

1. Initialization
   A spreadsheet has 26 columns (A–Z) and rows number of rows. Initially, all cells hold the value 0.

2. Set a cell
   setCell(cell, value) → Sets the value of the given cell.
   Example: A1 = 10.

3. Reset a cell
   resetCell(cell) → Resets a cell back to 0.

4. Evaluate a formula
   getValue(formula) → Evaluates a formula of the form =X+Y, where X and Y can be either:

   • A cell reference (like A1, B2)

   • A non-negative integer

   If a cell hasn’t been set yet, it is treated as 0.

🧩 Example

Input: ["Spreadsheet", "getValue", "setCell", "getValue", "setCell", "getValue", "resetCell", "getValue"] [[3], ["=5+7"], ["A1", 10], ["=A1+6"], ["B2", 15], ["=A1+B2"], ["A1"], ["=A1+B2"]] Output: [null, 12, null, 16, null, 25, null, 15]

👉 Explanation:

• =5+7 → 12

• A1=10 then =A1+6 → 16

• B2=15 then =A1+B2 → 25

• Reset A1=0 → =A1+B2 → 15

🎯 How to Approach

When solving this problem, the key idea is to simulate cell operations in a simple way:

1. Storage
   Use a map/dictionary to store cell values.
   Example: { "A1": 10, "B2": 15 }

2. Setting a cell
   Just update the map with the new value.

3. Resetting a cell
   Remove it from the map so that it’s treated as 0.

4. Evaluating a formula

   • Strip = sign and split by +.

   • Each part can be either:

     • A number → convert to integer.

     • A cell reference → fetch from the map (or 0 if not set).

   • Return the sum.

This approach ensures O(1) operations for set/reset/get.

⚡ Key Takeaways

• Real-world problems often boil down to simple data structures (like maps).

• Understanding input parsing (e.g., "=A1+5") is crucial in simulation problems.

• Don’t overcomplicate — keep it simple and efficient.

Video walkthrough

I recorded a short walkthrough explaining the idea and a step-by-step run of the example. Watch it here (or the embedded player below):

YouTube: https://youtu.be/GeAiJABwRNs

Closing notes

• This problem is a great mix of data-structure design and practical engineering trade-offs: "fast access" vs "fast arbitrary updates" — the Map + Heap pattern with lazy deletion is a pragmatic middle ground in JS.

Happy coding! 📚💻