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Finding position of an element in a two-dimensional array?

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终归单人心
终归单人心 2020-12-07 02:16

Well simple question here (maybe not a simple answer?)

Say I have a two dimensional array

[0] [1] [2]
[3] [4] [5]
[6] [7] [8]

Now s

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  • 星月不相逢
    星月不相逢 (楼主)
    2020-12-07 02:44

    Here is a method that should find an index in an array with an arbitrary rank.

    ... Added Upper/Lower bounds range per rank

    public static class Tools
{
    public static int[] FindIndex(this Array haystack, object needle)
    {
        if (haystack.Rank == 1)
            return new[] { Array.IndexOf(haystack, needle) };

        var found = haystack.OfType()
                          .Select((v, i) => new { v, i })
                          .FirstOrDefault(s => s.v.Equals(needle));
        if (found == null)
            throw new Exception("needle not found in set");

        var indexes = new int[haystack.Rank];
        var last = found.i;
        var lastLength = Enumerable.Range(0, haystack.Rank)
                                   .Aggregate(1, 
                                       (a, v) => a * haystack.GetLength(v));
        for (var rank =0; rank < haystack.Rank; rank++)
        {
            lastLength = lastLength / haystack.GetLength(rank);
            var value = last / lastLength;
            last -= value * lastLength;

            var index = value + haystack.GetLowerBound(rank);
            if (index > haystack.GetUpperBound(rank))
                throw new IndexOutOfRangeException();
            indexes[rank] = index;
        }

        return indexes;
    }
}

    
    
             
    
                                                        
    
            
            
    
              
                
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