Sort vector of vectors

Question

I have

    vector> vec 

in my c++ app.

Every vector of integers as an element of \"big\" vector has 4 INT valu

Answer 1

Sure it is. std::sort can take a third parameter which is the comparison function to use when sorting. For example, you could use a lambda function:

std::vector> vec;
// Fill it

std::sort(vec.begin(), vec.end(),
          [](const std::vector& a, const std::vector& b) {
  return a[2] < b[2];
});

Alternatively, you can pass anything else callable with signature bool(const std::vector&, const std::vector&), such as a functor or function pointer.

---

Response to edit: Simply apply your COST function to a and b:

std::sort(vec.begin(), vec.end(),
          [](const std::vector& a, const std::vector& b) {
  return COST(a) < COST(b);
});