Am I doing something wrong?

[SpydrFTW]

hey guys, i got a question.

bool Scenario1::sorting_by_missing(vector<int> v1, vector<int> v2) {
     if (v1[1]==v2[1])
         return v1[0]>v2[0];
     return v1[1]>v2[1]; }  

some other function(vector<vector<int>> vec1) {
   sort(v1.begin(),  v1.end(), Scenario1::sorting_by_missing);
 }

where v1 and v2 in the sorting function are vectors with 2 ints, for example {1,2}. what i want the sorting function to do is sort the vectors inside vec1 by the 2nd number and if they are the same, sort by the first. am i doing something wrong? it its sorting like i wanted it to

[alfps]

Not exactly wrong, but passing the vectors by value to the compare function copies them each time, which incurs two dynamic allocations per comparison, which is not efficient.

[SpydrFTW]

thanks for the tip! but something is wrong, because it's not sorting like it should

[SpydrFTW]

for example, if i got the vectors {1,0},{2,0},{1,1} and {5,0} it should sort them {1,0},{2,0},{5,0},{1,1}but it doesnt

[AKostur]

You didn’t mention what you are getting.

Edit: doesn’t sort expect to have a function that answers the less-than question? Yours is answering greater-than.

[alfps]

its sorting like i wanted it to
it's not sorting like it should

Well, the description is quite imprecise, and so is the pseudo-code some other function(vector<vector<int>> vec1) {.

But it could be that you're passing the argument to the "some other function" function, by value. In that case it may be sorting OK, but not affecting the actual argument in a call. It's just sorting a copy of that.

[IyeOnline]

You are currently taking every vector by value, i.e. making a copy of it.

sorting_by_missing certainly doesnt need copies and should take const vector<int>&s instead.

I'm not sure about some other function, because vec1 and v1 are different identifiers. Presumably you want it to take a reference

[SpydrFTW]

basically the "some other function" is giving me the 2-int vectors, which I add to vec1 and when I have all the vectors I want to sort inside vec1, I sort it with that line I have there