lower_bound()

lower_bound() is a function in the C++ standard library that returns an iterator pointing to the first element in a sorted range that is not less than a specified value. This function is used to perform binary search on a sorted range and returns the iterator to the first occurrence of the specified value or the iterator to the position where the value can be inserted in the range while maintaining the sorted order.

The syntax for the lower_bound() function is:

std::lower_bound(start_iterator, end_iterator, value);

where `start_iterator` and `end_iterator` are the iterators defining the range to be searched and `value` is the value to be searched for.

The lower_bound() function uses a binary search algorithm to find the first element in the range that is not less than the specified value. It returns an iterator to this element, which can be used to access the element or insert a new element at the appropriate position while maintaining the sorted order of the range.

If the specified value is greater than all the elements in the range, the function returns the end iterator of the range. If the range is not sorted, the behavior of the function is undefined.