如何在c ++中使用指向结构的指针向量？

I have an assignment that is due about a week from now. It is about making a letter counter (cases don't matter) of text file in the directory the source file is. Then the output of the letters should be, first, according to the letter with highest number of occurrences of it, and, second, if there are letters with the same number of occurrences, then sorting will be according to the alphabetical order. The assignment page is here: I have an assignment that is due about a week f