Exercise 1-12. Write a program that prints its input one word per line.
对应于自己练习的kr_10.c
Exercise 1-13. Write a program to print a histogram of the lengths of words in its input. It is
easy to draw the histogram with the bars horizontal; a vertical orientation is more challenging.
未做
Exercise 1-14. Write a program to print a histogram of the frequencies of different characters
in its input.