Medium data structure and algorithm practice puzzle.
Given a grid's rows and columns, return how many paths go from the top-left to the bottom-right moving only right or down. Use recursion. From any cell, the number of paths is the paths from the cell below plus the paths from the cell to the right. Reaching the goal counts 1, and stepping off the grid counts 0.
Solve it three ways: snap the jigsaw pieces together, fill in the blanks, or type it from scratch against the tests. This one is free.
Every line of the solution comes with a note explaining why it is there, and a step by step replay shows the code running. At level 3, where you type it yourself, you can ask for an AI mock interview on this problem that ends with a hiring manager's scorecard.
Then grow it into a real project with the Software Engineer button: this puzzle becomes the Frame Capacity Planner, a pipeline you can run and download. See every Software Engineer project.
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