Good morning! Here's our prompt for today.

We have a string str like the following:

1const str = "bubble";

Find a way to convert it to a palindrome by inserting characters in front of it. Recall that a palindrome is defined as "a word, phrase, or sequence that reads the same backward as forward".

What's the shortest palindrome that can be returned? For example, the following above string should return:

1shortestPalindrome("bubble")
2// "elbbubble"

Constraints

• Length of the given string <= 1000
• The string can contain any ASCII letters
• Expected time complexity : O(n)
• Expected space complexity : O(1)

Try to solve this here or in Interactive Mode.

How do I practice this challenge?

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def shortestPalindrome(s):

    # fill in

    return ""

​

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import unittest

​

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class Test(unittest.TestCase):

    def test_1(self):

        assert shortestPalindrome("bubble") == "elbbubble"

        print("PASSED: `shortestPalindrome('bubble')` should return `'elbbubble'`")

​

    def test_2(self):

        assert shortestPalindrome("dasndsadmx") == "xmdasdnsadasndsadmx"

        print(

            "PASSED: `shortestPalindrome('dasndsadmx')` should return `'xmdasdnsadasndsadmx'`"

        )

​

​

if __name__ == "__main__":

    unittest.main(verbosity=2)

    print("Nice job, 2/2 tests passed!")

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Here's our guided, illustrated walk-through.

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