Description : Returns the bounds of the subrange that includes all the elements of the range [[first, last) with values equivalent to passed value.
Example:
std::vector<int> vec = {1, 2, 3, 1, 6, 1};
// equal_range requires a sorted input {1, 1, 1, 2, 3, 6}
std::sort(vec.begin(), vec.end());
// returns pair of iterators for positions 0 and 2:
// {1, 1, 1, 2, 3, 6}
// ^ ^
auto equalRangeIt = std::equal_range(vec.begin(), vec.end(), 1);
for (auto it = equalRangeIt.first; it != equalRangeIt.second; ++it) {
std::cout << " Position: " << (it - vec.begin()) << " = " << *it << std::endl;
}