Bài giảng lập trình c 2010 chương 4 đh công nghệ đồng nai

• Programmer specifies the type of the elements of the array• new operator to allocate dynamically the number of elements in the array • Array declarations and initializations need not

Multi Dimension Array

5 2 9 7 6 0 8

- Same name

- Same type

- Get Element by Index ( 0 n-1)

One Dimension Array

• Programmer specifies the type of the elements of the array

• new operator to allocate dynamically the number of elements in the array

• Array declarations and initializations need not be in the same statement

• In arrays of value types, each element contains one value of the declared type

Declaring & Creating Arrays

int M1 [] =new int [ 10 ] ;

for ( int i=0;i<M1.Length;i++)

• array_name.Length: return size of array

• array_name GetValue ( int index): return an object at position index.

• array_name[ int index]: return an object at position index.

• array_name SetValue ( object value, int index): add or modify an object at position

index

• array_name[ int index] = value: add or modify an object at position index

Properties & Methods

Passing Arrays to Method

• Pass arrays as arguments to methods by specifying the name of the array (no brackets)

• Individual array elements are passed by value

static void inputArray(int[] arr)

{

Random ran = new Random();

arr[i] = ran.Next(100);

}

Passing Arrays to Method

Using out or ref keyword to pass by reference

static void edit( out int n)

The out parameter must be assigned to before control leaves the current method

static void edit(out int n)

{

//n = -113;

}

 Compile error

edit( out arr[0]);

edit( ref arr[0]);

Two ways: arr[0] -113

Use out keyword:

Use ref keyword:

arr[0]=100;

arrName = new DataType [ rowSize , colSize ];

DataType [ , ] arrName =

new DataType [ rowSize , colSize ];

int[,] M = new int[2, 2];

M[0, 0] = 1; M[0, 1] = 2;

M[1, 0] = 5; M[1, 1] = 3;

int[,] M = { {1,8} , {2,5} };

GetLength(int dimension)int[,] M = {{1,8},{2,5},{1,1} };

row=M.GetLength(0); row=3

col=M.GetLength(1); col=2

int[, ,] M2 = new Int32[3, 4, 5];

x=M2.GetLength(0);x=3

y=M2.GetLength(1);y=4

z=M2.GetLength(2);z=5

for ( int i = 0; i < M.GetLength(0); i++)

Arrays of Arrays

When we want to create a multi Array with different size:

- The first, we declare size of row, so each row will hold an array with any

size

- The second, We will declare those array

- And Initialize value for each item in array

DataType[ ][ ] arrName = new DataType[Size][ ];

int [][] K = new int [3][];

Array Class

Provides methods for creating, manipulating, searching, and sorting arrays, thereby serving as the base class for all arrays in the common language runtime.

CreateInstance(Type, Int32 [])

Creates a multidimensional Array of the specified Type and dimension

lengths, with zero-based indexing The dimension lengths are specified in an

array of 32-bit integers

// Creates and initializes a new two-dimensional Array of type

Int32.

(2 rows, 3 cols) Array myArr = Array CreateInstance( typeof ( Int32 ),2, 3);

for ( int i = myArr.GetLowerBound(0);

TO get value foreach item:

for ( int i = myArr.GetLowerBound(0);

a 32-bit integer

int[] myArr = new int[5] { 1, 2, 3, 4, 5 };

Object[] myObjArr = new Object[5] { 26, 27, 28, 29, 30 };

Copy 2 element from myArr to myObjArr:

Array.Copy(myArr,myObjArr,2) ;

Searches an entire one-dimensional sorted Array for a specific element, using the

object ( not found =-1)

int[] M = new int[5] { 1, 2, 3,

4, 5 };

int found=Array.BinarySearch(M, 8);

Method Description

using the IComparable implementation of each element of the Array

int[] M1 = new int[]{1,9,2,7,8};

Array.Sort(M1);

Out put: 1 2 7 8 9

ArrayList Class

dynamically increased as required

Constructors Description

that is empty and has the default initial capacity

ArrayList arrList = new

Constructors Description

that is empty and has the specified initial capacity

ArrayList arrList = new

Initializes a new instance of the ArrayList class that contains elements copied from the specified collection and that has the same initial capacity

as the number of elements copied

ArrayList arr1=new ArrayList();

arr1.AddRange( new int [] { 1, 1, 4 });

ArrayList arr2 = new ArrayList(arr1);

Method Description

Add Adds an object to the end of the ArrayList

ArrayList arr=new ArrayList();

arr.Add(1);arr.Add( "a" );arr.Add( 9 );

foreach (object item in arr)

Console.Write(item+“ ”);

//Output : 1 a 9

Method Description

ArrayList

ArrayList arr=new ArrayList();

arr.AddRange( new int [] { 1, 1, 4 });

foreach (int value in arr)

Console.Write(value+" ");

//Output : 1 1 4

Method Description

index.

ArrayList arr=new ArrayList();

arr.AddRange( new int [] { 1, 1, 4 });

arr.Insert(1, "teo" );

foreach (object value in arr)

Console.Write(value+" ");

//Output : 1 teo 1 4

InsertRange Inserts the elements of a collection into the ArrayList

at the specified index

ArrayList arr= new ArrayList();

arr.AddRange( new int [] { 1, 1, 4 });

ArrayList arrIns= new ArrayList();

Remove Removes the first occurrence of a specific object from the

RemoveRange Removes a range of elements from the ArrayList

ArrayList arr = new ArrayList();

arr.AddRange(new object[]

{ 1, "teo", 4, "ti" });

arr.RemoveRange(1, 2);

//1 is Start Index to remove

//2 is number of element to remove

foreach ( object value in arr)

Console Write(value + " " );

//Output : 1 ti

Method Description

ArrayList arr=new ArrayList();

Contains Determines whether an element is in the ArrayList

arr.AddRange( new string [] { "Chi" , "Pheo" , "Thi" , "No" });

bool bFound = arr.Contains("No");

IndexOf Searches for the specified Object and returns the zero-based

index of the first occurrence within the entire ArrayList

ArrayList arr = new ArrayList ();

arr.AddRange( new string [] { "Chi" , "Pheo" , "Thi" , "No" });

int pos1 = arr.IndexOf("Pheo" );

Console WriteLine( "Pos1=" +pos1);

//Output : Pos1=1

int pos2 = arr.IndexOf(“Teo" );

Console WriteLine( "Pos2=" +pos2);

//Output : Pos2=-1

Method Description

index of the last occurrence within the entire ArrayList

arr.AddRange(new string[] { “Teo", "Pheo", "Thi",

“Teo" });

int pos = arr.LastIndexOf(“Teo");

Console.WriteLine("Pos="+pos);

//Output : Pos=3

Sort Sorts the elements in the entire ArrayList

ArrayList arr = new ArrayList();

BinarySearch Searches the entire sorted ArrayList for an element using the

default comparer and returns the zero-based index of the element

ArrayList arr = new ArrayList();

Clone Creates a shallow copy of the ArrayList

ArrayList arr = new ArrayList();

What’s happen when We use Clone method???

ArrayList arr = new ArrayList();

CopyTo Copies the entire ArrayList to a compatible one-dimensional

Array, starting at the beginning of the target array

arr.Add(1);arr.Add( "a" );arr.Add( 9 );

object []M1= new object [arr.Count];

foreach ( object val in M1)

Console Write(val + " " );

//Output : 1 a 9

Method Description

arr.Add(1);arr.Add( "a" );arr.Add( 9 );

arr.Reverse();

foreach ( object val in M1)

Console Write(val + " " );

//Output : 9 a 1

Dictionary< TKey , TValue >

Represents a collection of keys and values

 Each addition to the dictionary consists of a value

and its associated key.

close to O(1).

 Every key in a Dictionary <TKey, TValue > must be

unique according to the dictionary's equality

comparer

 A key cannot be null , but a value can be, if the value

type TValue is a reference type

 The capacity is automatically increased as required

by reallocating the internal array

 Use KeyValuePair <TKey, TValue > structure representing

a value and its key.

Dictionary <TKey, TValue >()

Description:

> class that is empty, has the default initial capacity, and

uses the default equality comparer for the key type

// Create a new dictionary of ArrayList, with string keys.

Dictionary < string , ArrayList >

Dictionary < string , ArrayList >();

// Or

);

Add ( TKey key, TValue value )

Description:

Adds the specified key and value to the dictionary.

arr.Add("Nhà");arr.Add("Chỗ ở");

ArrayList aItem= myDIC["Home"];

foreach ( KeyValuePair<string,

{

string strKey = item.Key;

}

KeyValuePair <TKey, TValue>

Defines a key/value pair that can be set or retrieved

public bool ContainsKey (TKey key)

Description:

contains the specified key

if (myDIC.ContainsKey("Home"))

{

MessageBox.Show(“Có home");

}

public bool ContainsValue

(TValue value )

Description:

contains a specific value

if (myDIC.ContainsValue(arr))

{MessageBox Show( "Có Arr này rồi" );

}

public bool TryGetValue

(TKey key, out TValue value )

Description:

Gets the value associated with the specified key

ArrayList arr = null ;

if (myDIC.TryGetValue( "Home" , out arr))

{ //Process arr here

}

else { //Could not Get value

}

public bool Remove (TKey key )

Description:

Removes the value with the specified key from the

Dictionary <TKey, TValue>.

myDIC Remove ( "Home" );

Count

Description:

Gets the number of key/value pairs contained in the

Dictionary <TKey, TValue >

Item ( indexer)

Description:

Gets or sets the value associated with the specified key

KeyNotFoundException=>The property is retrieved and key does not exist in

the collection

ArgumentNullException=>key is null

myDIC["Home"]=arr (Arraylist);

Description:

Gets a collection containing the keys in the

myDIC.Keys;

foreach (string s in keyColl)

}

Description:

Gets a collection containing the values in the

myDIC.Values;

foreach(ArrayList arr in valColl)

{//Process value here

}

END