sort 2D string vector by selected column

[poopcupine]

Hi all, I am trying to sort my 2D vector by a selected column.
My 2D string vector:

a	Wed Feb 13 07:59:50 SGT 2019	2	0	nil
b	Wed Feb 13 07:59:04 SGT 2019	5	0	nil
c	Wed Feb 13 07:59:02 SGT 2019	3	2	nil
d	Wed Feb 13 07:58:49 SGT 2019	7	2	nil
e	Wed Feb 13 07:58:40 SGT 2019	9	111	nil
f	Wed Feb 13 07:58:32 SGT 2019	5	3	nil
g	Wed Feb 13 07:58:24 SGT 2019	6	111	nil
h	Wed Feb 13 07:58:21 SGT 2019	8	0	nil
i	Wed Feb 13 07:59:33 SGT 2019	14	9	nil

My code:

	int m = parsedCsv.size();
	int n = parsedCsv[0].size();

	const int columnId = 3;
	std::sort(parsedCsv.begin(), parsedCsv.end(), [&columnId](const std::vector<std::string> &item1, const std::vector<std::string> &item2)
	{
		return item1[columnId] < item2[columnId];
	});

	for (int i = 0; i < m; i++)
	{
		for (int j = 0; j < n; j++)
			cout << parsedCsv[i][j] << ",";
		cout << endl;
	}

Current output:

a,Wed Feb 13 07:59:50 SGT 2019,2,0,nil,
b,Wed Feb 13 07:59:04 SGT 2019,5,0,nil,
h,Wed Feb 13 07:58:21 SGT 2019,8,0,nil,
e,Wed Feb 13 07:58:40 SGT 2019,9,111,nil,
g,Wed Feb 13 07:58:24 SGT 2019,6,111,nil,
c,Wed Feb 13 07:59:02 SGT 2019,3,2,nil,
d,Wed Feb 13 07:58:49 SGT 2019,7,2,nil,
f,Wed Feb 13 07:58:32 SGT 2019,5,3,nil,
i,Wed Feb 13 07:59:33 SGT 2019,14,9,nil,

As you can see, the third column is not sorting as intended. Whats the issue here? Any response is appreicated

[lastchance]

It's sorting fine!

You are comparing strings, not integers. On that basis, "111" < "2".
Use std::stoi if you genuinely want to convert them to integers before comparing.

[poopcupine]

Thanks for your reply! How may I go about doing that by just converting one column?

[JLBorges]

const auto cmp_int = [] ( const std::string& a, const std::string& b )
{
    if( a.size() < b.size() ) return true ;
    else if( a.size() > b.size() ) return false ;
    else return a < b ;
};

std::sort( parsedCsv.begin(), parsedCsv.end(), [=]( const auto& item1, const auto& item2 )
{
    return cmp_int( item1[columnId], item2[columnId] ) ;
});

[poopcupine]

It worked. Thank you very much!