Question

Im doing an task atm. which I should compare all of the vector elements in an given range, in two different vector, for almost equal with help of STL algorithm.

Almost equal in this situation: 2.

Anyone know an solution for this problem?

Answer 1

If you want less-than comparison, use std::lexicographical_compare with a custom comparator implementing whatever it is that almost equal means for you.

If you want equality comparison, use std::equal, as pointed out in the comments:

bool comp(int a, int b) {
  return std::abs(a-b) <= 2;
}

int main() {

  std::vector<int> v0{2,3,4,5,5,5};
  std::vector<int> v1{6,7,8,9,8,7};
  std::cout << std::boolalpha;
  std::cout << std::equal(v0.begin(), v0.end(), v1.begin(), comp);

}

This is a simplified comparison function to show how to use the algorithm, you would have to decide what to do if the vectors have different length.