C # common algorithm questions (interview preparation)

1. Write the bubble, select, and insert the sorting algorithm.

// Bubble sort
Public class bubblesorter
{

Public void sort (int [] list)
{
Int length = list. Length;
For (int I = 0; I <length; I ++)
{

For (int j = length-1; j> I; j --)
{
If (list [j-1]> list [j])
{
Int temp;
Temp = list [j];
List [j] = list [j-1];
List [j-1] = temp;
}
}
}
}

}
// Select sorting
Public class selectionsorter
{
Private int min;
Public void sort (int [] list)
{
For (int I = 0; I <list. Length-1; I ++)
{
Min = I;
For (int j = I + 1; j <list. Length; j ++)
{
If (list [j] <list [min])
Min = j;
}
Int t = list [min];
List [min] = list [I];
List [I] = t;
}
}
}
// Insert sorting
Public class insertionsorter
{
Public void sort (int [] list)
{
For (int I = 1; I <list. Length; I ++)
{
Int t = list [I];
Int j = I;
While (j> 0) & (list [j-1]> t ))
{
List [j] = list [j-1];
-- J;
}
List [j] = t;
}
}
}
2. The number of columns is 30th, 5.

Public class MainClass
{
Public static void Main ()
{
Console. WriteLine (Foo (30 ));
}
Public static int Foo (int I)
{
If (I <= 0)
Return 0;
Else if (I> 0 & I <= 2)
Return 1;
Else return Foo (I-1) + Foo (I-2 );
}
}

3. Program Design: when the cat shouted, all the mice started to escape and the host was awakened.

Public delegate void SubEventHandler ();
Public abstract class Subject
{
Public event SubEventHandler SubEvent;
Protected void FireAway ()
{
If (this. SubEvent! = Null)
This. SubEvent ();
}
}
Public class Cat: Subject
{
Public void Cry ()
{
Console. WriteLine (cat cryed .);
This. FireAway ();
}
}
Public abstract class Observer
{
Public Observer (Subject sub)
{
Sub. SubEvent + = new SubEventHandler (Response );
}
Public abstract void Response ();
}
Public class Mouse: Observer
{
Private string name;
Public Mouse (string name, Subject sub): base (sub)
{
This. name = name;
}
Public override void Response ()
{
Console. WriteLine (name + attempt to escape !);
}
}
Public class Master: Observer
{
Public Master (Subject sub): base (sub ){}
Public override void Response ()
{
Console. WriteLine (host waken );
}
}
Class Class1
{
Static void Main (string [] args)
{
Cat cat = new Cat ();
Mouse mouse1 = new Mouse (mouse1, cat );
Mouse mouse2 = new Mouse (mouse2, cat );
Master master = new Master (cat );
Cat. Cry ();
}

}
4. There is a string "I am a good man". Design a function and return "man good a am I ".

5. Five students A, B, C, D, and E may participate in computer competitions. Which of the following conditions can be determined?
Participants:

(1) When A participates, B also participates;

(2) B and C are attended by only one person;

(3) Both C and D participate, or none;

(4) At least one of D and E participates;

(5) If E participates, both A and D participate.

Static void Main (string [] args)
{

Char [] name =... {'A', 'B', 'C', 'D', 'E '};
Int [] value = new int [5];
For (value [0] = 0; value [0] <2; value [0] ++)
For (value [1] = 0; value [1] <2; value [1] ++)
For (value [2] = 0; value [2] <2; value [2] ++)
For (value [3] = 0; value [3] <2; value [3] ++)
For (value [4] = 0; value [4] <2; value [4] ++)
{
If (value [1]> = value [0]) & (value [1] + value [2] = 1) & (value [2] = value [3]) & (value [3] + value [4] = 1) & (value [4] = 0 | value [4] = 1 & value [0] = 1 & value [3] = 1 ))
{
For (int I = 0; I <5; I ++)
{
If (value [I] = 1)
{
Console. WriteLine ("{0} participate", name [I]);
}
Else
{
Console. WriteLine ("{0} do not participate", name [I]);
}
}
}
}
}
6. Question:
A user entered an integer value into a text box. Without using a buit-in library, convert the numeric string to its integer representation.

Static int StringTolnt (string s)
{
Int sum = 0;
For (int I = 0; I <s. Length; I ++)
Sum = sum * 10 + (s [I]-'0 ');
Return sum;
}