1 // 17.9 Given a book, find out the occurrences of any given words in it.
 2 // Answer:
 3 //    1. process the book as a text file.
 4 //    2. find all words, definition of a word must be clearly asserted.
 5 //    3. use map or hash table to record the occurrences of words.
 6 //    4. query the statistics for an answer.
 7 int main()
 8 {
 9     return 0;
10 }