// Preliminary Part about Code Similarity+
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//========================================+
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+
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object CW7a {+
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+
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+
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//(1) Complete the clean function below. It should find+
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//    all words in a string using the regular expression+
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//    \w+  and the library function+
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//+
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//         some_regex.findAllIn(some_string)+
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//+
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//    The words should be Returned as a list of strings.+
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+
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+
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//def clean(s: String) : List[String] = ...+
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def clean(s: String) : List[String] =+
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    "\\w+".r.findAllIn(s).toList+
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+
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//(2) The function occurrences calculates the number of times+
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//    strings occur in a list of strings. These occurrences should+
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//    be calculated as a Map from strings to integers.+
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+
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+
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//def occurrences(xs: List[String]): Map[String, Int] = ..+
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def occurrences(xs: List[String]) : Map[String, Int] =+
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    xs.groupBy(identity).view.mapValues(_.size).toMap+
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+
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//(3) This functions calculates the dot-product of two documents+
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//    (list of strings). For this it calculates the occurrence+
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//    maps from (2) and then multiplies the corresponding occurrences.+
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//    If a string does not occur in a document, the product is zero.+
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//    The function finally sums up all products.+
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+
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+
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//def prod(lst1: List[String], lst2: List[String]) : Int = ..+
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def prod(lst1: List[String], lst2: List[String]) : Int =+
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    occurrences(lst1).map(x => occurrences(lst2).getOrElse(x._1, 0) * x._2).reduce(_ + _)+
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+
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//(4) Complete the functions overlap and similarity. The overlap of+
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//    two documents is calculated by the formula given in the assignment+
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//    description. The similarity of two strings is given by the overlap+
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//    of the cleaned strings (see (1)).+
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+
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+
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//def overlap(lst1: List[String], lst2: List[String]) : Double = ...+
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def overlap(lst1: List[String], lst2: List[String]) : Double =+
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    prod(lst1, lst2).toDouble/Math.max(prod(lst1, lst1).toDouble, prod(lst2, lst2).toDouble)+
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//def similarity(s1: String, s2: String) : Double = ...+
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def similarity(s1: String, s2: String) : Double =+
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    overlap(clean(s1), clean(s2))+
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+
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+
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/* Test cases+
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import CW7a._+
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val list1 = List("a", "b", "b", "c", "d")+
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val list2 = List("d", "b", "d", "b", "d")+
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occurrences(List("a", "b", "b", "c", "d"))+
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occurrences(List("d", "b", "d", "b", "d"))+
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prod(list1,list2) // 7+
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overlap(list1, list2)   // 0.5384615384615384+
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overlap(list2, list1)   // 0.5384615384615384+
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overlap(list1, list1)   // 1.0+
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overlap(list2, list2)   // 1.0+
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// Plagiarism examples from+
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// https://desales.libguides.com/avoidingplagiarism/examples+
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val orig1 = """There is a strong market demand for eco-tourism in+
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Australia. Its rich and diverse natural heritage ensures Australia's+
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capacity to attract international ecotourists and gives Australia a+
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comparative advantage in the highly competitive tourism industry."""+
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val plag1 = """There is a high market demand for eco-tourism in+
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Australia. Australia has a comparative advantage in the highly+
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competitive tourism industry due to its rich and varied natural+
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heritage which ensures Australia's capacity to attract international+
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ecotourists."""+
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similarity(orig1, plag1) // 0.8679245283018868+
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// Plagiarism examples from+
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// https://www.utc.edu/library/help/tutorials/plagiarism/examples-of-plagiarism.php+
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val orig2 = """No oil spill is entirely benign. Depending on timing and+
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location, even a relatively minor spill can cause significant harm to+
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individual organisms and entire populations. Oil spills can cause+
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impacts over a range of time scales, from days to years, or even+
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decades for certain spills. Impacts are typically divided into acute+
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(short-term) and chronic (long-term) effects. Both types are part of a+
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complicated and often controversial equation that is addressed after+
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an oil spill: ecosystem recovery."""+
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val plag2 = """There is no such thing as a "good" oil spill. If the+
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time and place are just right, even a small oil spill can cause damage+
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to sensitive ecosystems. Further, spills can cause harm days, months,+
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years, or even decades after they occur. Because of this, spills are+
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usually broken into short-term (acute) and long-term (chronic)+
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effects. Both of these types of harm must be addressed in ecosystem+
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recovery: a controversial tactic that is often implemented immediately+
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following an oil spill."""+
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overlap(clean(orig2), clean(plag2))  // 0.728+
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similarity(orig2, plag2)             // 0.728+
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// The punchline: everything above 0.6 looks suspicious and+
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// should be investigated by staff.+
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*/+
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+
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}+
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