Algorithm · Reddit · Hard
You have a string s and are allowed to prepend characters to it, but you may not insert characters anywhere else. Produce the shortest palindrome obtainable under that rule. Examples Example 1: Input: s = "aacecaaa" Output: aaacecaaa Example 2: Input: s = "abcd" Output: dcbabcd Constraints 0 <= s.length <= 5 * 10^4 Every character in s is a lowercase English letter.
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