Append cheaply — practice exercise

What you'll be asked to do

1. 1.Append cheaplyexercise · easy · 10 min

   Push a value onto the end and show the array joined by dashes.

   Passes when: #out should show 1-2-3.

2. 2.Remove from the endexercise · easy · 10 min · practice plan

   Pop the last value and show what remains, joined by dashes.

   Passes when: #out should show 4-5.

3. 3.Insert in the middleexercise · easy · 10 min · practice plan

   Use splice to insert 9 between the two values and show the result.

   Passes when: #out should show 1-9-2.

4. 4.Build without copyingexercise · easy · 10 min · practice plan

   Collect three doubled values into an array using push, then join them.

   Passes when: #out should show 2-4-6.

5. 5.Preallocate a rowexercise · medium · 10 min · practice plan

   Create an array of four zeros and show it joined by dashes.

   Passes when: #out should show 0-0-0-0.

6. 6.Fix unshift used to appendbug fix · easy · 8 min

   unshift adds to the front and shifts everything along.

   Passes when: #out should show 1-2-3.

7. 7.Fix shift used to drop the last valuebug fix · easy · 8 min · practice plan

   shift removes the first element, not the last.

   Passes when: #out should show 4-5.

8. 8.Fix splice deleting instead of insertingbug fix · easy · 8 min · practice plan

   The delete count is one, so it replaces rather than inserts.

   Passes when: #out should show 1-9-2.

9. 9.Fix the copy inside the loopbug fix · easy · 8 min · practice plan

   Rebuilding the array every pass is quadratic and loses the values here.

   Passes when: #out should show 2-4-6.

10. 10.Fix the array with a holebug fix · medium · 8 min · practice plan

    Assigning past the end leaves an empty slot that joins as nothing.

    Passes when: #out should show 0-0-0-0.

Between them these tasks cover Operation costs, push vs unshift and Avoiding copies.

Looking for a different chapter? See every practice set, or switch to the interview theory questions.