property "Name" get cfw_ return this.name; / Setter of the property
"Name" set cfw_ this.name = value; public string Color cfw_ / Getter of the
property "Color" get cfw_ return this.color; / Setter of the property
"Color" Chapter 11. Creating and Usin
120 Recursion or Iteration? The calculation of factorial is often given as
an example when explaining the concept of recursion, but in this case, as
in many others, recursion is not the best approach. Very often, if we are
given a recurrent definition of
by marking it as visited (with the character 's'). After that we recursively
search for a path in the four possible directions. After returning from the
recursive search of the four possible directions, we step back from the
current cell and mark it as av
to itself from within its own method body. By means of recursion we can
solve complicated combinatorial problems, in which we can easily
exhaust different combinatorial configurations, e.g. generating
permutations and variations and simulating nested loop
a tool for building the objects. What Is a Class? The class defines
abstract characteristics of objects. It provides a structure for objects or a
pattern which we use to describe the nature of something (some object).
Classes are building blocks of OOP an
position recursively, i.e. the current depth of recursion. In order to work
correctly, our program has to increment the counter when entering
recursion and save the direction we have taken in the position in the
array. When returning from a recursion, the
in .NET CLR system for cleaning the memory (garbage collector) which
takes care of releasing unused objects instead of us. Objects to which
there is no reference in the program at certain moment are automatically
released and the memory they take up is re
following result: Found the exit! Found the exit! Found the exit! You can
see that the exit has been found exactly three times. It seems that the
algorithm works correctly. However, we are missing the printing of the
path as a sequence of positions. Chapt
you know from math. For example the polynomial (3x2 + x - 5) can be
represented as an array of the numbers cfw_-5, 1, 3. Bear in mind that it is
useful at the zero position to put the coefficient for x 0 (in our case -5),
at the first position the coeffic
nested loops from 1 to K, where N and K are entered by the user. The
result of the performance of the program should be equivalent to the
execution of following fragment: for (a1 = 1; a1 <= K; a1+) for (a2 =
1; a2 <= K; a2+) for (a3 = 1; a3 <= K; a3+) for
which uses objects and their interactions for building computer
programs. Thus an easy to understand, simple model of the subject area
is achieved, which gives an opportunity to the programmer to solve
intuitively (by simple logic) many of the problems, w
classes. Finally, we are going to get familiar with the term "namespaces"
how they help us, how to include them and use them. Classes and
Objects Over the last few decades programming and informatics have
experienced incredible growth and concepts, which
by the operator new. The newly created object is usually assigned to the
variable from type coinciding with the class of the Chapter 11. Creating
and Using Objects 391 object (this, however, is not mandatory read
chapter "Principles of ObjectOriented Prog
and Graphs. Your program should visit each cell at most once and
should be fast, even on large matrices (like 1,000 x 1,000). 13. The same
like the previous exercise: use DFS or BFS. By a recursive traversal or
BFS traversal, find the areas of neighbor ce
Factorial(n - 1); By using this method we can create an application,
which reads an integer from the console computes its factorial and then
prints the obtained value: RecursiveFactorial.cs using System; class
RecursiveFactorial cfw_ static void Main()
Sometimes its usage could considerably simplify the programming code
and its readability. Example of Recursion Lets consider the Fibonacci
numbers. These are the elements of the following sequence: 1, 1, 2, 3, 5,
8, 13, 21, 34, 55, 89, 144, Each element o
lab.GetLength(1), and the count of the rows is lab.GetLength(0). When
entering the recursive method for searching, firstly we check if we go
outside the labyrinth. In this case the searching is terminated, because
going outside the boundaries of the labyr
can be obtained from the first k1 numbers (by taking the k th number or
omitting it). Bear in mind that in the general case all possible sums of
the numbers from the input array may be an awful lot. For instance,
possible sums of 50 int numbers in the ran
an example of a real-world definition of a class. Lets return to the
example with the dog. We would like to define a class Dog that models
the real object "dog". The class is going to include characteristics which
are common for all dogs (such as breed an
Programming". Now we will focus on objects as a basic concept in OOP.
386 Fundamentals of Computer Programming with C# What Is an
Object? We are going to introduce the concept object in the context of
OOP. Software objects model real world objects or abst
the moment we should remember that before proceeding with recursive
implementation we should think about an iterative variant, after which
we should choose the better solution according to the situation. Lets
look at another example where we could use rec
could use the algorithm described above. For example, if the range of
numbers is from -50 to 50, then the least sum is -50*S and the greatest is
50*S. If the numbers in the input array are random and not limited in a
range, then the problem has no efficie
path"). Example input (empty labyrinth 3x3): static char[,] lab = cfw_ cfw_' ', ' ',
' ', cfw_' ', ' ', ' ', cfw_' ', ' ', 'e', ; 376 Fundamentals of Computer
Programming with C# Example output for the above labyrinth: Found
path to the exit: RRDLLDRR Fou
char[,] lab = cfw_ cfw_' ', '*', '*', ' ', ' ', cfw_' ', ' ', ' ', '*', ' ', cfw_'*', ' ', ' ', '*', 'e', ;
Example output: (there is no output) You can see that the output is
correct, but again we could add a more friendly message (for example
"No exit!"
Objects with Set Parameters Now we are going to consider a slightly
different variant of the example above in which we set parameters when
creating the object: Cat someCat = new Cat("Johnny", "brown"); In this
case we would like the objects someCat to rep
elements (from 0 to k-1); - The element p[k] participates in sum and the
remainder sum-p[k] is obtained from the rest of the elements (from 0 to
k-1). The implementation is not complex. Just calculate the recursive
formulas by recursive method. We should
http:/en.wikipedia.org/wiki/ Breadth-first_search. There are enough
explanations and sample code. In order to implement a queue in C#, just
an array or the .NET system class System.Collections.Generics.Queue.
For the elements of the queue you could use yo
recording it in the class fields. We are going to focus on them in the
chapter "Defining Classes"; - Methods they implement the
manipulation of the data. An Example Class We are going to give an
example of a class in C#, which contains the listed elements
we added one more parameter to the recursive method for searching path
to the exit of the labyrinth: the direction we have taken to in order to
reach the current position. This parameter has no meaning when going
from the starting position. For this reaso