How its output will be 6.
Unable to understand
hello @sarveshkrg
By the definition
The lower_bound() method in C++ is used to return an iterator pointing to the first element in the range [first, last) which has a value not less than val. This means that the function returns the index of the next smallest number just greater than that number.
there is no element greater than 15
hence end of container ie size of container is returned