21.1. Transformations of Arrays21.1.1. Retrieving keys and values21.1.2. Flipping, reversing, and shuffling21.1.3. Merging, padding, slicing, and splicing21.2. Stacks and Queues21.3. Translating between Variables and Arrays21.4. Sorting21.5. Printing Functions for Visualizing Arrays21.6. Summary