Kotlin Brain Teasers

Discussion

The two variables x and y both start out with a value of 1, and both increase by 1 on each iteration of the createRoutePlan loop—but the program’s output doesn’t contain a single line where x and y share the same value. Why do the two ways of counting loop iterations produce different outcomes?

Lambda List

The first important thing to understand about this puzzle is that the values we’re assembling via the buildList function aren’t Point objects—they’re lambda functions that will create Point objects.

You’d normally pass a new list item to add in parentheses: add(123) for a list of numbers, add("abc") for a list of strings, and so on. But in Puzzle 11, ​This Much Is True​, you learned that when you use a lambda expression as the rightmost ...