I am trying to sort a vector of coordinates. The vector has pointers to these coordinates. I want to sort them by x and by y. What I am currently thinking of how to do this is as follows make two copies of the vector and then sort them. I am unsure of the following two things: 1) How to make a copy of a vector of pointers 2) How to sort both the points by x and y in the vectors and ensure also that they are properly sorted as follows (1,4),(1,5)
I have been reading and trying to figure out if there were any built in functions but I am not sure if for example sort function would correctly sort the x and y properly orderwise.
Here is what I have so far and any help would be appreciated.
typedef struct{double x; double y;) pt;
vector<pt*>v1;
vector<pt*>*v2 = v1;
// allocate memory for the points and push_back on the vector
the vector would have the following points {(1,7),(4,4),(1,3),(-2,4)}
When sorted it for x, it would be X={(-2,4),(1,3),(1,7),(4,4)} and Y={(1,3),(-2,4),(4,4),(1,7)}
UPDATE:
I am currently at this stage but it is still not working... :(
bool compare(pt* m1, pt* m2){return(m1->x <= m2->x) && (m1->y <= m2->y);}
vector<pt*>v1_x = v1;
sort(v1_x.begin(), v1_x.end(), comparer);
It's fairly easy using a custom comparator to do the dereferencing, as well as ready-made lexicographic tuple comparison:
#include <algorithm>
#include <tuple>
#include <vector>
struct pt { double x, double y };
std::vector<pt*> v = /* ... */ ;
auto x = v, y = v; // copies
std::sort(x.begin(), x.end(),
[](pt * a, pt * b) -> bool
{ return std::tie(a->x, a->y) < std::tie(b->x, b->y); });
std::sort(y.begin(), y.end(),
[](pt * a, pt * b) -> bool
{ return std::tie(a->y, a->x) < std::tie(b->y, b->x); });
Of course the objects pointed to by the pointers must live at least as long as you're using the pointers in v, x and y.