Re: Sorting vectors (multi-dimensional array)

"(2b|!2b)==?" <>
Sun, 04 Jan 2009 09:40:16 +0000
<> wrote:

On Jan 4, 4:11 am, "(2b|!2b)==?" <> wrote:

I have a multi-dimentional array (for the purposes of this post - lets
assume the dimensionality = 2 (to keep things simple). The array
(implemented by vectors), consists of "columns", where each column is of
a particular data type (similar to a traditional database table).

I want to be able to sort the array by its columns (like in Excel or in
a databse). I need some pseudocode or code sippet that will show how I
can sort the table (i.e. vector of columns) by specified columns.

Ideally, the algorithm will be generic enough to apply to an
N-dimensional table.

The easiest thing to do is use std::sort:

And supply it with a predicate function that compares the columns of

A general predicate for multiple fields is usually something like (say
you want to sort by field1, then field2, then ..., then fieldN):

bool isbefore (const Thing &a, const Thing &b) {

  if (a.field1 < b.field1)
    return true;
  else if (b.field1 < a.field1)
    return false;
  else if (a.field2 < b.field2)
    return true;
  else if (b.field2 < a.field2)
    return true;
  // ... and so on ...
    return a.fieldN < b.fieldN;



Hi Jason, could you please elaborate some more?. I mean, suppose I have

class DataColumn
    std::string name;
    std::vector<Variant> m_rows ;

class MemoryTable
     void SortByColumns(const std::vector<std::string>& colnames);

    std::vector<DataColumn> m_cols ;

How would I go about implementing SortByColumns(), using std::sort and a
predicate function?

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