Slots of Fun
Time Limit: 2 Seconds
Memory Limit: 65536 KB
The International Betting Machine company has just issued a new type of slot
machine. The machine display consists of a set of identical circles placed in
a triangular shape. An example with four rows is shown below. When the player
pulls the lever, the machine places a random letter in the center of each circle.
The machine pays offwhenever any set of identical letters form the vertices
of an equilateral triangle. In the example below, the letters 'a' and 'c' satisfy
In order to prevent too many payoffs, the electronics in the machine ensures
that no more than 3 of any letter will appear in any display configuration.
IBM is manufacturing several models of this machine, with varying number of
rows in the display, and they are having trouble writing code to identify winning
configurations. Your job is to write that code.
Input will consist of multiple problem instances. Each instance will start with
an integer n indicating the number of rows in the display. The next line will
contain n(n + 1)/2 letters of the alphabet (all lowercase) which are to be stored
in the display row-wise, starting from the top. For example, the display above
would be specified as
The value of n will be between 1 and 12, inclusive. A line with a single 0 will
For each problem instance, output all letters which form equilateral triangles
on a single line, in alphabetical order. If no such letters exist, output "LOOOOOOOOSER!".
Source: East Central North America 2002