C # Getting Started basic grammar summary (Arrays and collections)

One, array

1, one-dimensional array creation:

array element data type [] array name; such as Int[]arr; String[] arr;

2. Initialization of one-dimensional arrays

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

②int[] Arr=new int[]{1,2,3};

③int[]arr={1,2,3};

3, two-dimensional array creation:

① the array of data type [,] array name int[,]a=new int[2,4];2 row 4 column. Fit Rule Array

② data type [] [] array name int[][] a=new int[2][];int[0]=new int[2]; represents the first row two columns. Int[1]=new Int[3]; represents the second row of three columns. Note: This type of naming method cannot specify the number of columns. Specify the number of columns for each row before specifying the number of rows

4. Initialization of two-dimensional arrays

①int[,] arr=new int[2,2]; arr[0,0]=0;arr[0,1]=1;

②int[][] Arr=new int[2][]; Arr[0]=new int[]{0,1};arr[1]=new int[]{1,2}; Note: Rows are determined first, and each row is a one-dimensional array.

③int[,] arr=new int[2,2]{{12,0},{45,10}}; int[,] arr=new int[]{{12,0},{45,10}};int[,] arr={{12,0},{45,10}};

Ii. operation of arrays

1. Input and output of one-dimensional arrays: using single-layer loops

2. Two-dimensional array input and output: using double loop

3. The Foreach method iterates through the array: foreach (int number in arr)

4, array of sorts: ascending sort () from small to large, reverse () reverse sort;

5, Bubble Sort: The basic idea compares the adjacent two numbers, satisfies the condition, the smaller number rows in the array front, the larger number row after the array. Need to use a double loop,//Outer loop represents the comparison wheel number, 5 number to compare 4 rounds.//within the cycle from the comparison of the number of comparisons, the first round compared 4 times, the second round compared 3 times.

6. Select Sort: The basic idea is to exchange elements that satisfy the conditions with the position of the element at the specified position. The two-layer for loop implementation, the outer loop compares the number of wheels. Each round to find a minimum value for the position swap. The inner Loop finds the index of the minimum value.

Third, ArrayList class

1, ArrayList three kinds of constructors:

① using the default constructor

ArrayList list=new ArrayList ();

for (int i=0;i<10;i++) {list.add ()}

② is constructed with a Icolliction object

ArrayList list=new ArrayList (arryname)

③ Initializes an internal array with the specified size

ArrayList list=new ArrayList (n);

2, the addition of ArrayList elements

①add method adds an element at the end

②insert method Insert (index,value) index, value

3. ArrayList element deletion

①clear method to remove all elements

The ②remove method removes the first object of a specified object, remove (OBJ)

③removeat method RemoveAt (int index)

④removerange (index,count) index starts the number of indexes that count is removed

4. ArrayList traversal Array

foreach ()

5, ArrayList elements of the search

①contains method Contains (OBJ)

②indexof method returns the first occurrence of the location

③lastindexof method where the last occurrence of a match occurs

Four, Hashtable class

1, the addition of Hashtable elements

Add (Key,value) key key value

2. Hashtable element Removal

①clear method

②remove method Remove (key)

3, Hashtable traversal using the Dictionnaryentry type

4, Hashtable elements of the search

①contains method Contains (key)

②containsvalue method Containsvalue (value)

C # Getting Started basic grammar summary (Arrays and collections)