You've just moved into a perfectly straight street with exactly n identical houses on either side of the road. Naturally, you would like to find out the house number of the people on the other side of the street. The street looks something like this:
1| |6
3| |4
5| |2
Evens increase on the right; odds decrease on the left. House numbers start at 1 and increase without gaps. When n = 3, 1 is opposite 6, 3 opposite 4, and 5 opposite 2.
Given your house number address and length of street n, give the house number on the opposite side of the street.
Examples
over_the_road(address, n)
over_the_road(1, 3) = 6
over_the_road(3, 3) = 4
Tests
over_the_road(3, 5)
over_the_road(7, 11)
Good luck!
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Top comments (4)
Simple solution:
Here is sample picture to explain all of this:
APL (using Dyalog APL):
(Use the bookmarklet on this post to see the code with APL font and syntax highlighting.)
Explanation: The sum of two houses facing each other is always the same for given
n, which is2n+1. So the opposite house number becomes2n+1-address.Ruby