[google大赛 入围赛250分真题] SongFilter

Problem Statement
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You have a collection of music files with names formatted as “genre-artist-album-song” (quotes for clarity only), where genre, artist, album, and song each consist of only lowercase letters (‘a’-'z’) and spaces (but no leading/trailing spaces). The collection is given in the String[] collection. You would like to filter the songs according to a set of criteria given in the String[] filterInfo. Each element of filterInfo is an equality check formatted as “field=value” (quotes for clarity only), where field is “genre”, “artist”, “album”, or “song”, and value consists of only lowercase letters (‘a’-'z’) and spaces (but no leading/trailing spaces). For a file to pass through the filter, it must satisfy every equality check in filterInfo. For example, if filterInfo = {“genre=country”, “album=greatest hits”}, only songs from country greatest hits albums should be returned. Return a String[] containing all the files that meet the given criteria in the same relative order as they appear in collection.
Definition
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Class:
SongFilter
Method:
filter
Parameters:
String[], String[]
Returns:
String[]
Method signature:
String[] filter(String[] collection, String[] filterInfo)
(be sure your method is public)
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Constraints
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collection will contain between 1 and 50 elements, inclusive.
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Each element of collection will be formatted as described in the problem statement.
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Each element of collection will contain between 7 and 50 characters, inclusive.
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Each genre, artist, album, and song in collection will contain between 1 and 20 characters, inclusive.
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collection will contain no duplicate elements.
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filterInfo will contain between 1 and 4 elements, inclusive.
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Each element of filterInfo will be formatted as described in the problem statement.
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Each value in filterInfo will contain between 1 and 20 characters, inclusive.
Examples
0)

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{“jazz-joe pass-virtuoso-cherokee”,
 ”rock-led zeppelin-ii-lemon song”,
 ”country-dwight yoakam-long way home-things change”,
 ”metal-iron maiden-powerslave-aces high”,
 ”pop-supremes-more hits-ask any girl”,
 ”rock-faith no more-angel dust-rv”,
 ”jazz-chuck mangione-feels so good-feels so good”,
 ”rock-van halen-ii-spanish fly”}
{“genre=rock”, “album=ii”}
Returns: {“rock-led zeppelin-ii-lemon song”, “rock-van halen-ii-spanish fly” }
This filter returns all the rock songs from albums with the title “ii”.
1)

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{“rock-jimi hendrix-axis bold as love-little wing”,
 ”rock-cars-cars-moving in stereo”,
 ”rock-jimi hendrix-electric ladyland-gypsy eyes”,
 ”blues-albert collins-ice pickin-ice pick”,
 ”rock-jimi hendrix-axis bold as love-bold as love”,
 ”rock-jimi  hendrix-axis bold as love-exp”}
{“artist=jimi hendrix”, “album=axis bold as love”}
Returns:
{“rock-jimi hendrix-axis bold as love-little wing”,
 ”rock-jimi hendrix-axis bold as love-bold as love” }
This filter returns all the songs that are from the album “axis bold as love” by the artist “jimi hendrix”. The last element in the collection is not returned because there are two spaces between “jimi” and “hendrix”.
2)

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{“rock-ozzy osbourne-blizzard of ozz-dee”,
 ”rock-marvelous three-hey album-let me go”,
 ”rock-cheap trick-in color-downed”}
{“genre=soul”}
Returns: { }
There is no soul music in this collection, so an empty String[] is returned.
3)

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{“country-topcoder-the country album-twangy”,
 ”rock-topcoder-the rock album-rockin”,
 ”jazz-topcoder-the jazz album-jazzy”,
 ”soul-topcoder-the soul album-soulful”,
 ”metal-topcoder-the metal album-thrash”}
{“artist=topcoder”, “genre=jazz”, “album=the jazz album”, “song=jazzy”}
Returns: {“jazz-topcoder-the jazz album-jazzy” }

4)

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{“pop-jackson five-abc-the love you save”,
 ”rock-ac dc-powerage-riff raff”}
{“genre=pop”, “genre=rock”}
Returns: { }
No single element of collection can represent more than one genre, so this filter returns an empty String[].
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