HackerEarth - Shil, and Palindrome Solution
Shil is your new boss and he likes palindromes very much. Palindrome is a string that can be read the same way in either direction, from the left to the right and from the right to the left. (ex. madam , aabaa, racecar)
Given a string S , beautiful Palindrome is a lexicographical minimum palindrome that can be formed by rearranging all the characters of string S. In order to please your boss, find a beautiful Palindrome that can be formed with help of string S.
String x is lexicographically less than string y, if either x is a prefix of y (and x ≠ y), or there exists such i (1 ≤ i ≤ min(|x|, |y|)), that xi < yi, and for any j (1 ≤ j < i) xj = yj. Here |a| denotes the length of the string a. The lexicographic comparison of strings is implemented by operator < in modern programming languages.
Only line of input contains string S. All the letters of this string will be in lower letters('a' - 'z').
Output lexicographical minimum Palindrome that can be formed by rearranging all the letters of string S. If no such Palindrome exist for given input, print -1.
After rearranging all the characters , all the palindromes that can be formed are cabac and acbca. Out of these two lexicographical minimum one is acbca.
Solution in Python
import sys from collections import Counter s = input().strip() c = Counter(s) pal = "" mid = "" odd = 0 for k,v in c.items(): if v%2: odd+=1 mid+=k v-=1 pal+=k*(v//2) if odd > 1 : print("-1") else: pal = "".join(sorted(pal)) print(pal+mid+pal[::-1])