{"id":30391,"date":"2023-01-14T19:03:12","date_gmt":"2023-01-14T13:33:12","guid":{"rendered":"https:\/\/jassweb.com\/solved\/solved-with-an-array-of-strings-of-equal-length-get-the-nth-character-of-each-string-in-its-own-array-using-linq\/"},"modified":"2023-01-14T19:03:12","modified_gmt":"2023-01-14T13:33:12","slug":"solved-with-an-array-of-strings-of-equal-length-get-the-nth-character-of-each-string-in-its-own-array-using-linq","status":"publish","type":"post","link":"https:\/\/jassweb.com\/solved\/solved-with-an-array-of-strings-of-equal-length-get-the-nth-character-of-each-string-in-its-own-array-using-linq\/","title":{"rendered":"[Solved] With an array of strings of equal length, get the nth character of each string in it’s own array using LINQ"},"content":{"rendered":"

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A quick test shows that setting @jdweng’s purely LINQ solution 1X, a solution somewhat abusing LINQ to do indexing comes in at 7.4X and a solution using for<\/code> comes in at 28.4X.<\/p>\n

(Ab)using LINQ with indexing:<\/p>\n

var c = Enumerable.Range(0, source[0].Length).Select(chpos => Enumerable.Range(0, source.Length).Select(si => source[si][chpos]).Join()).ToArray();\n<\/code><\/pre>\n
Using nested for<\/code> loops:<\/p>\n
var sourcelen = source.Length;\nvar strlen = source[0].Length;\nvar c = new String[strlen];\nvar sb = new StringBuilder(strlen);\nfor (int chpos = 0; chpos < strlen; ++chpos) {\n    for (int si = 0; si < sourcelen; ++si)\n        sb.Append(source[si][chpos]);\n    c[chpos] = sb.ToString();\n    sb.Length = 0;\n}\n<\/code><\/pre>\n
Running some further tests, Append<\/code> is a little faster then indexing the StringBuilder<\/code> until there are a lot of long strings and building all the strings in parallel (sequentially) isn’t faster, and as the strings increase in length, a Parallel.For<\/code> version catches up to the fastest nested for<\/code> version and then surpasses it, if you have a large number (10,000) of strings. Interestingly Append<\/code> is much slower than indexing in Parallel<\/code>.<\/p>\n
Here is the build each indexed parallel version:<\/p>\n
    var sourcelen = source.Length;\n    var strlen = source[0].Length;\n    var c = new String[strlen];\n    Parallel.For(0, strlen, chpos => {\n        var sb = new StringBuilder(sourcelen);\n        sb.Length = sourcelen;\n        for (int si = 0; si < sourcelen; ++si)\n            sb[si] = source[si][chpos];\n        c[chpos] = sb.ToString();\n    });\n<\/code><\/pre>\n
Using this Join<\/code> extension method greatly speeds up the solutions that use String.Join(String.Empty,<\/code> or String.Join(\"\",<\/code>:<\/p>\n
public static string Join(this IEnumerable<char> src) {\n    var sb = new StringBuilder();\n    foreach (var c in src)\n        sb.Append(c);\n    return sb.ToString();\n}\n<\/code><\/pre>\n
Some notes on timings: Using LINQPad, I wrote some code to generate a sample source<\/code>:<\/p>\n
var lens = 10000;\nvar source = new string[10000];\n\/\/\n{\n    var s = Enumerable.Range(0,26).Select(letternum => new String(Convert.ToChar('a'+letternum), lens)).ToArray();\n    for (int j1 = 0; j1 < source.Length; ++j1)\n        source[j1] = s[j1 % 26].ToString();\n}\n<\/code><\/pre>\n
Then, using LINQPad’s Util.ElapsedTime<\/code>, I measured the time to process source<\/code> with various implementations:<\/p>\n
TimeSpan basetime;\n\/\/\n{\n    var start = Util.ElapsedTime;\n    var c = source.Select(x => x.Select((y, i) => new { chr = y, index = i })).SelectMany(x => x).GroupBy(x => x.index).Select(x => x.Select(y => y.chr).Join()).ToArray();\n    basetime = Util.ElapsedTime - start;\n    basetime.Dump(\"Elapsed LINQ My Join 1X\");\n    \/\/c.Dump();\n}\n\/\/\n{\n    var start = Util.ElapsedTime;\n    var sourcelen = source.Length;\n    var strlen = source[0].Length;\n    var c = new String[strlen];\n    Parallel.For(0, strlen, chpos => {\n        var sb = new StringBuilder(sourcelen);\n        sb.Length = sourcelen;\n        for (int si = 0; si < sourcelen; ++si)\n            sb[si] = source[si][chpos];\n        c[chpos] = sb.ToString();\n    });\n    var myt = Util.ElapsedTime - start;\n    myt.Dump($\"Elapsed build each indexed parallel {basetime.TotalSeconds \/ myt.TotalSeconds:0.0}X\");\n    c.Dump();\n}\n<\/code><\/pre>\n<\/p><\/div>\n
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solved With an array of strings of equal length, get the nth character of each string in it’s own array using LINQ <\/p>\n","protected":false},"excerpt":{"rendered":"
[ad_1] A quick test shows that setting @jdweng’s purely LINQ solution 1X, a solution somewhat abusing LINQ to do indexing comes in at 7.4X and a solution using for comes in at 28.4X. (Ab)using LINQ with indexing: var c = Enumerable.Range(0, source[0].Length).Select(chpos => Enumerable.Range(0, source.Length).Select(si => source[si][chpos]).Join()).ToArray(); Using nested for loops: var sourcelen = source.Length; … Read more<\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[320],"tags":[361,324,578],"class_list":["post-30391","post","type-post","status-publish","format-standard","hentry","category-solved","tag-arrays","tag-c","tag-linq"],"yoast_head":"\n[Solved] With an array of strings of equal length, get the nth character of each string in it's own array using LINQ - JassWeb<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/jassweb.com\/solved\/solved-with-an-array-of-strings-of-equal-length-get-the-nth-character-of-each-string-in-its-own-array-using-linq\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"[Solved] With an array of strings of equal length, get the nth character of each string in it's own array using LINQ - JassWeb\" \/>\n<meta property=\"og:description\" content=\"[ad_1] A quick test shows that setting @jdweng’s purely LINQ solution 1X, a solution somewhat abusing LINQ to do indexing comes in at 7.4X and a solution using for comes in at 28.4X. 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