bool Account: : follow $($const string& username$)$;

This function is to return false if the invoking account is already following the username provided or the array is already at its capacity. No change shall then be made to any data member of the invoking account. Otherwise, it adds the username to the following$\_$ array data member, updates the nFollowing$\_$data member, and retums true.

bool Account: :unfollow $($const string& username$)$ ;

This function is to return false if the invoking account is not currently following the usemame provided. No change shall then be made to any data member of the invoking account. Otherwise, it removes the usemame from the following$\_$ array data member by shifting the related elements forward, updates the nFollowing$\_$data member, and returns true.

string Account:: get$\_$following$($const string& key $="")$ const ;

This function is to perform a keyword search through the following$\_$array and return a string of all matching usernames, formatted in a nice tabular format. You are required to use a stringstream object along with parametric manipulator to help you organize the format of the string to be returned. It shall not change any of the data members of the object. If no match is found, the function shall return an empty string.

By default, the value for key is an empty string, indicating the returned string of the function shall include all usernames in the following$\_$ array, from the oldest to the newest. However, if a non$-$empty string is presented for the key parameter, the returned string shall include only usernames containing the key as its substring.

For example, here is a sample output of cout $$ a$.$get$\_$following $()$ endl; showing the top $10$ tech influencers being followed:

ElonMusk JoannaStern GuyKawasak!

HarkZuckerberg

GrahamClutey

Larrykin

LewisHilsenteger

PaulAsadoorian

MarquesBrownlee GaryVaynerchuk

And here is a sample output of cout $$ a$,$get$\_$following $("$er$")$ endl; showing only those with the string $"$er$"$ as part of their names.

MarkZuckerberg

Levishtisenteger

Joannastern

GaryWaynerchuk