Benelux Algorithm Programming Contest 2005 sponsored by Sogeti

The Problems

Programming contests consist of about eight problems, each requesting you to program an algorithm that solves the problem. To give you an idea of what kind of problems are used at the contest, and how these problems are presented to you, we have provided the problem set used in the preliminary rounds for the BAPC 2005, as well as a sample problem - with a sample solution - from a contest held back in 1994.

The problems used in the contest round are available as a PDF file. The input, output, and sample solutions for both sessions are available as a gzipped tarball.

Test session
Problem	Sample input	Judge's input	Judge's output	Sample solution in C
A	a.in	a.in	a.out	a.c
B	b.in	b.in	b.out	b.c
C	c.in	c.in	c.out	c.c

Contest
				Sample solution
Problem	Sample input	Judge's input	Judge's output	C	C++	Java	Pascal
A	a.in	a.in	a.out	-	a.cpp	ProblemA.java	a.pas
B	b.in	b.in	b.out	b.c	b.cpp	ProblemB1.java ProblemB2.java	-
C	c.in	c.in	c.out	c.c	c.cpp	-	-
D	d.in	d.in	d.out	-	d.cpp	-	d.pas
E	e.in	e.in	e.out	e.c	e1.cpp e2.cpp	ProblemE1.java ProblemE2.java	-
F	f.in	f.in	f.out	-	f1.cpp f2.cpp	ProblemF.java	-
G	g.in	g.in	g.out	-	g.cpp	ProblemG.java	-
H	h.in	h.in	h.out	-	h.cpp	ProblemH.java	-

The problems used in these rounds are available as a PDF file. The sample input, input/output used by the judges, and sample solutions are also available as gzipped tarballs.

				Sample solution
Problem	Sample input	Judge's input	Judge's output	C++	Java	Pascal
A	a.in	a.in	a.out	a.cpp	-	a.pas
B	b.in	b.in	b.out	b.cpp	b.java	-
C	c.in	c.in	c.out	c.cpp	c.java	-
D	d.in	d.in	d.out	d.cpp	-	d.pas
E	e.in	e.in	e.out	e.cpp	-	e.pas
F	f.in	f.in	f.out	f.cpp	f.java	-
G	g.in	g.in	g.out	g.cpp	-	g.pas
H	h.in	h.in	h.out	h.cpp	-	h.pas

In the land of Hedonia the official language is Hedonian. A Hedonian professor
had noticed that many of her students still did not master the syntax of
Hedonian well. Tired of correcting the many syntactical mistakes, she decided to
challenge the students and asked them to write a program that could check the
syntactical correctness of any sentence they wrote. Similar to the nature of
Hedonians, the syntax of Hedonian is also pleasantly simple. Here are the
rules:

0. The only characters in the language are the characters p through z and N, C,
D, E, and I.

1. Every character from p through z is a correct sentence.

2. If s is a correct sentence, then so is Ns.

3. If s and t are correct sentences, then so are Cst, Dst, Est, and Ist.

4. Rules 0. to 3. are the only rules to determine the syntactical correctness
of a sentence.

You are asked to write a program that checks if sentences satisfy the syntax
rules given in Rule 0. - Rule 4.

Input:

The input consists of a number of sentences consisting only of characters p
through z and N, C, D, E, and I. Each sentence is ended by a new-line character.
The collection of sentences is terminated by the end-of-file character. If
necessary, you may assume that each sentence has at most 256 characters and at
least 1 character.

Output:

The output consists of the answers YES for each well-formed sentence and NO for
each not-well-formed sentence. The answers are given in the same order as the
sentences. Each answer is followed by a new-line character, and the list of
answers is followed by an end-of-file character.

Sample Input:

Cp
Isz
NIsz
Cqpq

Sample Output:

NO
YES
YES
NO

The input used to check contestant's solutions can be found here, the output that the solution should generate is behind this link, and here's a sample solution in C.