List of potential QOTW problems.

Write a program to notice repeated lines.

 
a
b
c
b
c
b
c
a
b
c
a
b
c
d
e
 becomes

 
a
b
c
(Last 2 lines repeated 2 times)
a
b
c
(Last 3 lines repeated 1 time)
d
e

Given a list of words known to be sorted into some order, generate a string consisting of letters in that order.