Given a string S consisting of lowercase characters(a-z) only, the task is to print a new string by rearranging the string in such a way that maximizes the number of palindromic substrings. In case of multiple answers, print any one.
Note: even if some substrings coincide, count them as many times as they appear in the obtained string.
Input: s = “aabab”
string “ababa” has 9 palindromic substrings: “a”, “b”, “a”, “b”, “a”, “aba”, “bab”, “aba”, “ababa”.
Input: s = “aa”
The given string has the maximum number of palindromic substrings possible, “a”, “a” and “aa”.
The problem might look to be a complex one but on solving for various cases and having observations will lead to an easy solution.
A simple solution is to sort the string and print it. Sorting takes O(N * log N).
An efficient solution is to count the frequency of each character using a freq array and then construct the string using the freq array.
Below is the implementation of the above approach.
# Python3 program to rearrange the
# string such to maximize the
# number of palindromic substrings
# Function to return the newString
# length of string
l = len(s)
# hashing array
freq =  * (26)
# iterate and count
for i in range(0, l):
freq[ord(s[i]) – ord(‘a’)] += 1
# resulting string
ans = “”
# form the resulting string
for i in range(0, 26):
# number of times character appears
for j in range(0, freq[i]):
# append to resulting string
ans += chr(97 + i)
# Driver Code
if __name__ == “__main__”:
s = “aabab”
# This code is contributed by Rituraj Jain
Time Complexity: O(N)
Auxiliary Space: O(26)
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