palindrome.py

# find a palindrome in just two (reasonable) or one unreasonable line of Python code
# Copyright Ryan Marcus and Can Nahum 2016


import collections
import functools



def getPalin(x):
    m = functools.reduce(lambda d,c: {k: v if k != c else v + 1 for (k, v) in d.items()}, # folds new value into dictionary
                         x, # for each character in the string
                         {k: 0 for (v,k) in enumerate(x)}) # start with all values = 0


    return (("".join([k*(int(v/2)) for (k, v) in m.items() if v % 2 == 0]) +
             "".join([k*v for (k, v) in m.items() if v % 2 == 1]) +
             "".join([k*(int(v/2)) for (k, v) in m.items() if v % 2 == 0])[::-1])
            if len({k: v for (k, v) in m.items() if v % 2 == 1}) <= 1 else -1)





    
if __name__ == "__main__":
    x = "bbccffggh"
    print(getPalin(x))