Five tasks. All of them are about memory layout, not syntax.

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1. InsertAt(items []Item, i int, it Item) []Item

Inserts it at position i and returns the new slice.

Count how many elements shifted. Do it for i = 0, i = n/2 and i = n. Which of the three is O(1), and why?

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2. DeleteAt(items []Item, i int) []Item

Deletes an element while preserving order.

Then write DeleteFast, which does not preserve order: it moves the last element into the gap and shortens the slice.

How many shifts does each cost? When is DeleteFast the wrong choice?

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3. Grow(n int) (reallocs, copied int)

Reproduce step 2's measurement without the algo command — just a function returning two numbers.

Then run it starting from make([]Item, 0, n), with the capacity reserved up front. How many reallocations do you get? Explain why.

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4. MemoryPerItem(n int) float64

Work out how many bytes per item are actually reserved when a slice holds n elements: cap × size / n.

Run it for n from 1 to 100. When is the ratio worst? Tie your answer back to the capacity sequence in step 2.

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5. The zero-value trap

What happens if you write lib := make([]Item, 1000) and then append to it?

Write a short program that shows it, and explain how make([]Item, 1000) differs from make([]Item, 0, 1000). This mistake gets made constantly.