How should I practice Merging Palindromes?

Start by reading the full statement, solve the visible examples, then compare the pattern against related Old Mission online assessment problems in FastPrep.

Is Merging Palindromes associated with Old Mission?

FastPrep tags this as a Old Mission online assessment coding practice problem when the problem catalog has that company and stage context.

Merging Palindromes

Old Mission● MediumFULLTIMEOA

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Problem statement

From the letters of first, choose a multiset that can be rearranged into a palindrome. Do the same independently for second. Combine the two chosen multisets and rearrange them into one palindrome.

Return the longest palindrome obtainable this way. If several have maximum length, return the lexicographically smallest.

Function

mergingPalindromes(first: String, second: String) → String

Examples

Example 1

first = "aabbc"second = "ddefefq"return = "abdefcfedba"

Use every available pair from both strings. Among the remaining odd-count letters, c is the smallest possible center, producing the lexicographically smallest maximum-length palindrome.

Example 2

first = "abc"second = "xyz"return = "a"

No character forms a pair in either string. A one-character palindrome is optimal, and a is lexicographically smallest.

Constraints

1 <= first.length, second.length <= 200000
Both strings contain lowercase English letters only.