如何优雅地实现 blowup 函数呢？

drunkedcat

blowup 函数的定义如下：

“abc” ->"abbccc"
"abcd" -> "abbcccdddd"
....

我写了个实现，但是觉得不太优雅，有没有更直接更优雅一些的写法呢？

blowup :: String -> String blowup [] = [] blowup xs = concat [take (fst x) (repeat (snd x)) | x <- zip [1..] xs]

drunkedcat

或者下面这个实现？

blowup2 :: String -> String blowup2 [] = [] blowup2 xs = (blowup2 . init) xs ++ take (length xs)  (repeat  (last xs) )

flw

blowup = concat . zipWith replicate [1..]

drunkedcat

flw 兄一出手，果然，佩服，学习ing.

win_hate

我也来一个

1. 
   
2. f (x:xs)= (return x) : (zipWith (:) xs (f xs))
   

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izhier

与一楼的类似

1. 
   
2. blowup xs = concat [take n (repeat c) | (c, n) <- zip xs [1..]]
   

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