📄️ Pattern 2: Grid Traversal Problems
The 2D Foundation Pattern: Move through 2D grid, build each cell from cells you've already visited (typically top/left).
📄️ 📘 Unique Paths - The Discovery Journey
How the human brain naturally discovers the DP solution
📄️ 🔴 Unique Paths - Unoptimized Recursive Solution
Understanding the naive approach and why it fails
📄️ 📘 Unique Paths - Plain English Proof
Why dpi = dpi-1 + dpi must be true, using everyday reasoning
📄️ 📘 Unique Paths - Formal Proof
Why dpi = dpi-1 + dpi is a mathematical certainty, not just a pattern
📄️ 🧩 Unique Paths II - The Discovery Journey
How to adapt your solution when constraints change: The obstacle challenge
📄️ 🧩 Unique Paths II - Plain English Proof
Why the formula still works with obstacles, explained using everyday reasoning
📄️ 🧩 Unique Paths II - Formal Proof
Why the recurrence relation still works with obstacles, and why setting obstacle cells to zero is mathematically sound
📄️ 🛤️ Minimum Path Sum: The Designer's Journey from Confusion to Clarity
From brute force chaos to elegant optimization - the path of discovery