How it works...

The whole program is constructed around the insert_sorted function, which does what this section is about: For any new string, it locates the position in the sorted vector, at which it must be inserted, in order to preserve the order of the strings in the vector. However, we assume that the vector was sorted before. Otherwise, this would not work.

The locating step is done by the STL function lower_bound, which accepts three arguments. The first two denote beginning and end of the underlying range. The range is our vector of words in this case. The third argument is the word, which shall be inserted. The function then finds the first item in the range, which is greater than or equal to that third parameter and returns an iterator pointing to it.

Having the right position at hand, we gave it to the std::vector member method insert, which accepts just two arguments. The first argument is an iterator, which points to the position in the vector, at which the second parameter shall be inserted. It appears very handy that we can use the same iterator, which just dropped out of the lower_bound function. The second argument is, of course, the item to be inserted.