I am able to solve this challenge but when look at my code I know it is not good.
Bill and Ted are taking a road trip. But the odometer in their car is broken, so they don’t know how many miles they have driven. Fortunately, Bill has a working stopwatch, so they can record their speed and the total time they have driven. Unfortunately, their record keeping strategy is a little odd, so they need help computing the total distance driven. You are to write a program to do this computation.
For example, if their log shows
Speed in miles per hour | Total elapsed time in hours
20 | 2
30 | 6
10 | 7
this means they drove 2 hours at 20 miles per hour, then 6−2=4 hours at 30 miles per hour, then 7−6=1 hour at 10 miles per hour. The distance driven is then 2⋅20+4⋅30+1⋅10=40+120+10=170 miles. Note that the total elapsed time is always since the beginning of the trip, not since the previous entry in their log.
The input consists of one or more data sets. Each set starts with a line containing an integer n, 1≤n≤10, followed by n pairs of values, one pair per line. The first value in a pair, s, is the speed in miles per hour and the second value, t, is the total elapsed time. Both s and t are integers, 1≤s≤90 and 1≤t≤12. The values for t are always in strictly increasing order. A value of −1 for nsignals the end of the input.
For each input set, print the distance driven, followed by a space, followed by the word “miles”.
3 20 2 30 6 10 7 2 60 1 30 5 4 15 1 25 2 30 3 10 5 -1
170 miles 180 miles 90 miles
I try to split the input to case-by-case group and solve it using
calculate but end-up with deep nested list.
import Data.List.Split main :: IO () main = do as <- map words . lines <$> getContents let bs = filter (not.null) $ splitWhen ((==1).length) as let cs = map (map (map (read :: String -> Int))) bs let ds = map calculate cs mapM_ putStrLn ds calculate :: [[Int]] -> String calculate xs = z where as = map head xs bs = map last xs cs = head bs : zipWith (flip (-)) bs (tail bs) ds = zipWith (*) as cs z = show (sum ds) ++ " miles"
The code is ugly especially on line 7:
map (map (map (read :: String -> Int)))
There are lot of
let and meaningless bindings (as, bs, ...) because I need to insert
print xs to see what the list is look like after each step.
Reading code again without
How should I make it better?