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# Make the string lexicographically smallest and non palindromic by swapping of adjacent pair of characters

• Last Updated : 07 Mar, 2022

Given string str consisting of lowercase alphabets, the task is to construct the lexicographically smallest non-palindromic string by swapping any pair of adjacent characters from the string any number of times.
If the given string cannot be converted to a lexicographically smallest non-palindromic string, then print “-1”.

Examples:

Input: str = “djfbw”
Output: bdfjw
Explanation:
Perform the following swap operations to get the lexicographically smallest non-palindromic string:
Swap ‘b’ and ‘f’, str becomes “djbfw”
Swap ‘j’ and ‘b’, str becomes “dbjfw”
Swap ‘b’ and ‘d’, str becomes “bdjfw”
Swap ‘j’ and ‘f’, str becomes “bdfjw”.
Now “bdfjw” is the lexicographically smallest string which is not a palindrome.

Input: str[] = “pppppp”
Output: -1

Naive Approach: The idea is to generate all possible permutations of the string and to check if they form palindrome or not. Print the smallest permutation among them.

Time Complexity: O(N*N!)
Auxiliary Space: O(N)

Efficient Approach: The idea is to check if lexicographically the smallest string possible from the given string is a palindrome or not. Below are the steps:

1. To obtain lexicographically the smallest string, sort the given string to arrange the characters of the string in increasing order.
2. Now, if the sorted string is a palindrome, then it means that the string has only one type of character and it can not be arranged to form a string which is not a palindrome.
3. If it is not a palindrome, then the sorted string is lexicographically the smallest string which is not a palindrome.

Below is the implementation of the above approach:

## C++

 `// C++ program for the above approach` `#include ``using` `namespace` `std;` `// Function to find the lexicographically``// smallest string which is non-palindrome``void` `smallestNonPalindromic(string& s)``{` `    ``// Sort the given string``    ``sort(s.begin(), s.end());` `    ``// Store reverse of sorted string``    ``string reversestring``        ``= string(s.rbegin(), s.rend());` `    ``// Check if the sorted string is``    ``// palindromic or not``    ``if` `(s != reversestring) {``        ``cout << s;``    ``}``    ``else` `{``        ``cout << ``"-1"``;``    ``}``}` `// Driver Code``int` `main()``{``    ``// Given string str``    ``string str = ``"asmfjdeovnhekfnj"``;` `    ``// Function Call``    ``smallestNonPalindromic(str);``    ``return` `0;``}`

## Java

 `// Java program for the above approach``import` `java.util.*;``class` `GFG{` `// reverse string``static` `String reverse(String input)``{``  ``char``[] a = input.toCharArray();``  ``int` `l, r = a.length - ``1``;``  ``for` `(l = ``0``; l < r; l++, r--)``  ``{``    ``char` `temp = a[l];``    ``a[l] = a[r];``    ``a[r] = temp;``  ``}``  ``return` `String.valueOf(a);``}` `// Method to sort a string alphabetically``static` `String sortString(String inputString)``{``  ``// convert input string to char array``  ``char` `tempArray[] = inputString.toCharArray();` `  ``// sort tempArray``  ``Arrays.sort(tempArray);` `  ``// return new sorted string``  ``return` `new` `String(tempArray);``}``  ` `// Function to find the lexicographically``// smallest String which is non-palindrome``static` `void` `smallestNonPalindromic(String s)``{``  ``// Sort the given String``  ``s = sortString(s);` `  ``// Store reverse of sorted String``  ``String reverseString = reverse(s);` `  ``// Check if the sorted String is``  ``// palindromic or not``  ``if` `(s != reverseString)``  ``{``    ``System.out.print(s);``  ``}``  ` `  ``else``  ``{``    ``System.out.print(``"-1"``);``  ``}``}` `// Driver Code``public` `static` `void` `main(String[] args)``{``  ``// Given String str``  ``String str = ``"asmfjdeovnhekfnj"``;` `  ``// Function Call``  ``smallestNonPalindromic(str);``}``}` `// This code is contributed by gauravrajput1`

## Python3

 `# Python3 program for the above approach` `# Function to find the lexicographically``# smallest string which is non-palindrome``def` `smallestNonPalindromic(s):` `    ``# Sort the given string``    ``s ``=` `sorted``(s)` `    ``# Store reverse of sorted string``    ``reversestring ``=` `s[::``-``1``]` `    ``# Check if the sorted string is``    ``# palindromic or not``    ``if` `(s !``=` `reversestring):``        ``print``("".join(s))``    ``else``:``        ``print``(``"-1"``)` `# Driver Code``if` `__name__ ``=``=` `'__main__'``:``    ` `    ``# Given string str``    ``str` `=` `"asmfjdeovnhekfnj"` `    ``# Function call``    ``smallestNonPalindromic(``str``)` `# This code is contributed by mohit kumar 29`

## C#

 `// C# program for the above approach``using` `System;` `class` `GFG{` `// Reverse string``static` `String reverse(String input)``{``    ``char``[] a = input.ToCharArray();``    ``int` `l, r = a.Length - 1;``    ` `    ``for``(l = 0; l < r; l++, r--)``    ``{``        ``char` `temp = a[l];``        ``a[l] = a[r];``        ``a[r] = temp;``    ``}``    ``return` `String.Join(``""``, a);``}` `// Method to sort a string alphabetically``static` `String sortString(String inputString)``{``    ` `    ``// Convert input string to char array``    ``char` `[]tempArray = inputString.ToCharArray();``    ` `    ``// Sort tempArray``    ``Array.Sort(tempArray);``    ` `    ``// Return new sorted string``    ``return` `new` `String(tempArray);``}` `// Function to find the lexicographically``// smallest String which is non-palindrome``static` `void` `smallestNonPalindromic(String s)``{``    ` `    ``// Sort the given String``    ``s = sortString(s);``    ` `    ``// Store reverse of sorted String``    ``String reverseString = reverse(s);``    ` `    ``// Check if the sorted String is``    ``// palindromic or not``    ``if` `(s != reverseString)``    ``{``        ``Console.Write(s);``    ``}``    ``else``    ``{``        ``Console.Write(``"-1"``);``    ``}``}` `// Driver Code``public` `static` `void` `Main(String[] args)``{``    ` `    ``// Given String str``    ``String str = ``"asmfjdeovnhekfnj"``;``    ` `    ``// Function call``    ``smallestNonPalindromic(str);``}``}` `// This code is contributed by Amit Katiyar`

## Javascript

 ``

Output:

`adeeffhjjkmnnosv`

Time Complexity: O(N)
Auxiliary Space: O(1)

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