CS · Week 3
Repeating work, storing lists, and common off-by-one mistakes.
An array (or list) stores values in order. Indexing usually starts at 0, so the last item is length − 1.
A for loop is good when you know how many times to repeat. A while loop repeats until a condition is false.
Off-by-one errors happen when you use < vs ≤, or forget that the last index is length − 1.
Trace a loop on paper with a tiny list. If you can predict each step, the code is easier to debug.