Permutation of string, Haskell -

this question exact duplicate of:

• permutations 1 symbol back, haskell [closed] 1 answer

i have given string: abcdpqrs, output be: badcqpsr.

my current code:

f :: [a] -> [a] f (a:b:xs) = b:a:xs f xs = xs 

evaluating f "abcdpqrs" results in "bacdpqrs". how can used "badcqpsr"?

try processing more first 2 characters recursing on remainder of list:

f :: [a] -> [a] f (a:b:xs) = b:a:f xs f xs = xs