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

DONG NAI UNIVERSITY OF TECHNOLOGY


DONG NAI UNIVERSITY OF TECHNOLOGY

1

One Dimension Array

2

Multi Dimension Array

3

Array class

4

ArrayList class

5

Dictionary class


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One Dimension Array
M[0]

5

M[1]

2

M[2]

M[3]

9

7

M[4]

6

- Same name
- Same type
- Get Element by Index ( 0 n-1)

M[5]

0

M[6]

8

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Declaring & Creating Arrays

•

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


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Declaring:

<DataType> [ ] <ArrayName>;
int [ ] M;
Button[ ] arrButton;

Creating:
<ArrayName> =new <DataType>[ ARRAY_SIZE];

M=new int[10];
Button []arrButton=new Button[10];


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Examples…
int M1[]=new int[10];
for(int i=0;iM1[i]=i*2;
for(int i=0;iConsole.Write(M1[i] + “”);
foreach(int value in M1)
Console.Write(value + “”);
int M2[]={1,4,2} ;


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•
•
•
•

Properties & Methods
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


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Passing Arrays to Method

•

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

•
•

Arrays are passed by reference
Individual array elements are passed by value


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Passing Arrays to Method
static void inputArray(int[] arr)
{
Random ran = new Random();
for (int i = 0; i

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


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Using out or ref keyword to pass by reference
static void edit(out int n)
{
n = -113;
}

OR:
static void edit(ref int n)
{
n = -113;
}


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The out parameter must be assigned to before control leaves the current
method
static void edit(out int n)
{
//n = -113;
}
 Compile error

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arr[0]=100;
Use out keyword:
edit(out arr[0]);
Use ref keyword:
edit(ref arr[0]);

Two ways: arr[0] -113


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7

2

9

0

9

5

4

1

8

0

3

6

Multi Dimension


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Column 0

Column 1

Column 2

Column 3

M[0, 0]

M[0, 1]

M[0, 2]

M[0, 3]

7

2

9

0

M[1, 0]

M[1, 1]

M[1, 2]

M[1, 3]

9

5

4

1

M[2, 0]

M[2, 1]

M[2, 2]

M[2, 3]

8

0

3

6

Row 0

Row 1

Row 2

Column index (or subscript)
Row index (or subscript)
Array name


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DataType[ , ] arrName;
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} };


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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


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

{
for (int j = 0; j < M.GetLength(1); j++)

{
Console.Write(M[i,j] +" ");
}
Console.WriteLine();
}

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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][ ];


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int[][] K = new int[3][];
K[0] = new int[] { 1,3};
K[1] = new int[] { 9};
K[2] = new int[] { 5, 4, 9 };
for (int i = 0; i < K.GetLength(0); i++)
{
for (int j = 0; j < K[i].Length; j++)
{
Console.Write(K[i][j] +" ");
}
Console.WriteLine();
}

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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.


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Method
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.


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// 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);
i <= myArr.GetUpperBound(0); i++)
for (int j = myArr.GetLowerBound(1);
j <= myArr.GetUpperBound(1); j++)
{
myArr.SetValue(i+j, i, j);
}

DONG NAI UNIVERSITY OF TECHNOLOGY

TO get value foreach item:
for (int i = myArr.GetLowerBound(0);
i <= myArr.GetUpperBound(0); i++)
{
for (int j =
myArr.GetLowerBound(1);
j <= myArr.GetUpperBound(1); j++)
{
Console.Write(
myArr.GetValue(i, j) + " ");
}
Console.WriteLine();
}


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Method

Description

Copy(Array, Array,

Copies a range of elements from an Array starting at

Int32)

the first element and pastes them into another Array
starting at the first element. The length is specified as
a 32-bit integer


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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) ;