DAY 66 OF 90 · Walk the grid

Flip rows and columns

Medium90 Days of Looping

Inputs

cells is a grid: a list of 1 to 5 rows, each with the same number (1 to 5) of whole numbers from -9 to 9.

Your tasks

Create an empty list flipped.
Use an outer loop over the columns. For each column c, build a row by walking down every row of cells and taking its cth number. Add row to flipped.
Complete transpose so it returns flipped. Return it, do not print it.

Example

With cells = [[1, 2, 3], [4, 5, 6]], transpose returns [[1, 4], [2, 5], [3, 6]].

Rules

A grid with 2 rows and 3 columns becomes a grid with 3 rows and 2 columns.

Test data

TEST DATA 1: cells is [[1, 2, 3], [4, 5, 6]]

TEST DATA 2: cells is [[7]]

Practice focus

Two-dimensional data is a loop over rows with a loop over columns inside. Grids lead straight to flood fill, islands, dynamic programming tables and path problems.

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