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Thread: Determing if one string is a rotation of another

  1. #1
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    Default Determing if one string is a rotation of another

    Hi,
    I have an assignment for my computer science 1 class I could really use some help on. Here's exactly what it says:

    Assume you have a method isSubstring which checks if one word is a substring of another, ex: isSubstring("water", "ter") returns true.
    Given two strings s1 and s2, write code to check if s2 is a rotation of s1 using isSubstring, ex: "waterbottle" is a rotation of "erbottlewat"

    I figured a way to put all the characters into an array and then just shuffle the order one letter at a time and compare that to the original. Problem is that the code has to use the isSubstring method mentioned. Any ideas?


  2. #2
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    Default Re: Determing if one string is a rotation of another

    You need to find where a substring of the first String is a substring of the second String. For example:

    Is waterbottle a substring of erbottlewat? No.
    Is aterbottle a substring of erbottlewat? No.
    Is terbottle a substring of erbottlewat? No.
    Is erbottle a substring of erbottlewat? Yes.

    Now you have a location you can chop the first String in two at that location, concatenate them back together in the opposite order and compare to the second String.
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