C # Collection Types--array, ArrayList, List

In the study or work, the collection is often used, you can change the words "No Item no Collection", "Project has a collection." It typically stores a series of data or carries out a series of data related operations. Here is a brief discussion of some collection types related to the review.

Arrays (Array)

Arrays typically store only one type of data, one-dimensional arrays, two-dimensional arrays, and so on. are based on the System.Array class.

Format: type[] typename; type refers to types, typename index group names.

One-dimensional arrays have several forms of writing:

int [] a={1,2,3};

int [] B=new int[]{1,2,3};

int [] C; C=new int[]{1,2,3};

int [] d=new int[3];d [0]=1;d[1]=2;d[2]=3;

Two-dimensional arrays: equivalent to tables

int[,] e=new int[2,2]; e[0,0]=1;e[0,1]=2;e[1,0]=3;e[1,1]=4;//two rows and two columns

int[,] f=new int[2,2]{{1,2},{3,4}};//number of rows known

int[,] f=new int[,]{{1,2},{3,4}};//unknown number of rows, according to the following initialization to specify the number of rows

Three-dimensional analogy, equivalent to the Quartet body.

Jagged arrays: equivalent to each element of a one-dimensional array is an array. An array of arrays, often called.

int[][] h=new int [2][]{new int[]{2,4,6},new int[]{1,2,3,4,5}};

Int[][] i=new int[][]{new int[]{2,4,6},new int[]{1,2,3,4,5}};

Int[][] j={new int[]{2,4,6},new int[]{1,2,3,4,5}};

int[][] k=new int[2][]; k[0]=new int[3]{2,4,6}; k[1]=new int[5]{1,2,3,4,5};

Then, k[0][0]=2;k[0][1]=4;k[1][2]=3;

int[][,] m=new int [2][,]

{New int[,] {{1,3},{5,7}},new int[,]{{0,2},{4,6}}}

Array Common operations

(1) iterating through an array

int [] a={1,2,3};

foreach (int n in a) {Console.WriteLine (n); }

Result Output 1 2 3

(2) converting between array strings

String[] sarr1={"123", "456", "789"};

String Str1=sarr1.join (",", sArr1);//The result is a string: 123,456,789

String[] Sarr2=str1. Split (', ');//The string is converted to a string array, removing the delimiter "," and converting the dimension array

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String str2= "ABC 12,65;8"

string [] sarr2=str2. Split (', ', ', '; ');

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String s= "13MNNFSJ";

Char[] A=s.tochararray (); \ \ Converts the string to a char array.

(3) Common functions

Int[] a={1,2,3,4};

A.sum ();//sum; A.average ();   A,min (); A.max ();

(4) Sorting, copying, finding

int []a={1,2,3};

int []b=new int[a.length];

Array.copy (a,b,a.length);//Copy the A array to the B array

Array.Sort (a);//array A in ascending order

Array.reverse (a);//reverse Sort a array

Use the Contains method and the IndexOf method to find the specified element.

ArrayList class

Equivalent to an advanced dynamic array. Using System.Collections.Generic; it is more advanced than an array, can delete and add elements dynamically, and its capacity can be expanded, but it has only one-dimensional form. Generally there are three ways of construction.

One, the default size (16) to initialize

ArrayList arr=new ArrayList ();

Second, add a collection element to the ArrayList

Int[] A=new int[]{1,2,3};

ArrayList arr1=new ArrayList (a);

Three, specify the size to initialize,

ArrayList arr2=new ArrayList (+);

Common properties: Slightly, in VS, for example, enter the above arr2. The properties and descriptions are displayed.

Common methods

Int[] A=new int[]{1,2,3};

ArrayList arr1=new ArrayList (a);

(i) Increased

1,add (Element), method,

Arr1. ADD (7);//ARR1 element is 1 2 3 7

2,insert (index, Element); method//index starting from 0

Arr1. Insert (1,7);//arr1 element is 1 7 2 3

(ii) deletion

1,clear () method//Delete all

Arr1. Clear ();//arr1 is empty.

2.Remove (Match Object) method//Remove first match object

Arr1. Remove (3);//arr1 element is 1 2

3,removeat (Index) method//delete the element corresponding to the index

Arr1. RemoveAt (1);//arr1 element is 1 3

4,removerange (index, Range) method//delete a range of numbers from the index

Arr1. RemoveRange,//arr1 element is 1

(iii) traversal

Same as Array

(d) Find

Contains (Element);

Arr1. contain (3);//Determine if arr1 contains 3 of this element, contains, is true; not included as False

List

Using System.Collections.Generic; It is a mistake that ArrayList the type, improves the encoding quality, and is less of a type. Here is a brief explanation of the usage of the General list, which will be studied in depth later on in the use of generic lists.

List <int> lis1=new list<int> ();

(i) Add

Lis1. Add (500);//Adds a string of elements directly

List1. AddRange (New int[]{501,502});//Add a string of elements.

(b) Insert, Delete, find and so on a series of operations similar to the above ArrayList and array.

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The specified type can also be a custom type, such as:

1, foresight a person class

Class Person {
public string name;
public string Name {
Get{return name;}
set {value = name;}
}
}

2, create Person object

Person p = new person ();
P.name = "Chen";
person P1 = new person ();
P1.name = "Li";
person P2 = new person ();
P2.name = "Zhang";

3, create a collection of person types and put the Perosn object in the collection

List <person>li=new list<person> ();
Li.add (P);
Li.add (p1);
Li.add (p2);

Console.WriteLine (li[0].name);//The first element of the output collection, with the result: Chen.

C # Collection Types--array, ArrayList, List