# Find a palindromic string B such that given String A is a subsequense of B

Given a string . Find a string , where B is a palindrome and A is a subsequence of B.

A subsequence of a string is a string that can be derived from it by deleting some (not necessarily consecutive) characters without changing the order of the remaining characters. For example, “cotst” is a subsequence of “contest”.

A palindrome is a string that reads the same forward or backward.

Examples:

```Input : A = "aba"
Output : B = aba
Explanation : "aba" is a subsequence of "aba"
which is a palindrome.

Input : A = "ab"
Output : B = abba
```

## Recommended: Please try your approach on {IDE} first, before moving on to the solution.

Approach: Let reverse(s) be the reverse of a string . Now, s + reverse(s) will always have as a subsequence (as first half) and it is a palindrome.

Therefore, B = A + reverse(A).

Below is the implementation of the above approach:

 `# Python program to find a palindromic string B ` `# such that given String A is a subsequense of B ` ` `  `# Function to check if a string is palindrome ` `def` `checkPalindrome(s): ` `    ``# Reversing a string ` `    ``x ``=` `s[::``-``1``] ` `    ``# check if reversed string is equal  ` `    ``# to given string ` `    ``if``(x ``=``=` `s): ` `        ``return` `True` `    ``else``: ` `        ``return` `False` `         `  `# Function to find a palindromic string B ` `# such that given String A is a subsequense of B ` `def` `findStringB(A): ` `     `  `    ``# Reversing the string A ` `    ``B ``=` `A[::``-``1``] ` `     `  `    ``B ``=` `B ``+` `A ` `     `  `    ``# If the string A is already a palindrome ` `    ``# return A ` `    ``if``(checkPalindrome(A)): ` `        ``return` `A ` `       `  `    ``# else return B     ` `    ``return` `B ` ` `  `# Driver Code ` `A ``=``"ab"` `print``(findStringB(A)) `

Output:

```baab
```

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