C # static variable usage,

C # static variable usage,

You can use static modifiers to declare static members that belong to the type rather than specific objects. static modifiers can be used for classes, fields, methods, attributes, operators, events, and constructors, but it cannot be used for any type other than the indexer, destructor, or class.

 

Static global variables

Definition: Before the global variable, add the keyword static. This variable is defined as a static global variable.

Features: A. The variable allocates memory in the global data zone. B. Initialization: If Explicit initialization is not performed, the value 0 is implicitly initialized.

 

Static local variables

Definition: When the static keyword is added before the local variable, the static local variable is defined.

Features: A. The variable allocates memory in the global data zone. B. Initialization: If Explicit initialization is not performed, the value 0 is implicitly initialized. C. It always resides in the global data zone until the program is running. But its scope is local scope. When the function or statement block defining it ends, its scope ends.

Static Data Member
Features: A. Memory Allocation: it is allocated in the global data zone of the program. B. Initialization and definition: space must be allocated when defining static data members. Therefore, space cannot be defined in the class declaration. B. In order to avoid repeated definitions in multiple source files using this class, it cannot be defined in the Class header file. C. static data members must exist at the beginning of the program running, so their initialization is best implemented within the class. C. feature a. The effect of the public, protected, and private keywords is the same as that of common data members. B. Because its space is allocated in the global data zone, all objects of this class are shared. Therefore, it does not belong to a specific class object. When no class object is generated, its scope is visible. That is, when no class instance is generated, we can operate on it.
D. Access Form a. Class Object Name. static data member name

E. static data members are mainly used for attributes owned by all instances of the class. For example, for a deposit type, the account is different from each instance, but the interest of each instance is the same. Therefore, the interest should be set as the static data member of the deposit class. There are two advantages: first, no matter how many deposit-type objects are defined, interest data members share the memory allocated in the global zone, thus saving storage space. Second, once the interest needs to change, the interest of all deposit objects will change once, because they actually share one thing.

Static member functions
Features: A. static member functions are associated with classes, but not with class objects. B. static member functions cannot access non-static data members. The reason is simple. Non-static data members belong to specific class instances.
Function: Used to operate static data members.

Call form: A. Class Object Name. static member function name ()

 

Static variable instances and Analysis

 Instance:

C # code Replication

 using System;

namespace teststatic

{    class class1    {        static int i = getNum();        int j = getNum();         static int num = 1;                static int getNum()        {            return num;        }         static void Main(string[] args)        {            Console.WriteLine("i={0}",i);            Console.WriteLine("j={0}", new class1().j);            Console.Read();        }    }}

 

Analyze the above Code:

Console. writeLine (string. format ("I = {0}", I); here I is a static variable, and class class1 is used for the first time. First, allocate memory for all static variables in class1. Despite the hyperthread technology, the logic of commands is still executed one by one in order. Therefore, the memory is allocated for static int I and the default value of int is 0 in the memory, then allocate memory for the static int num variable. The value is also 0.

Then execute the second step and assign values to the variable: assign values to the static int I variable first, And I = getNum (). Check the code in getNum, that is, return num. At this time, the value of num is 0, so I is 0. Then assign the value to the variable num, num = 1; after this line of code is executed, num is 1.

So the final result is:

I = 0 j = 1

A simple program of C language Bubble Sorting

Main ()
{
Int I, j, temp;
Int a [10];
For (I = 0; I <10; I ++)
Scanf ("% d,", & a [I]);
For (j = 0; j <= 9; j ++)
{For (I = 0; I <10-j; I ++)
If (a [I]> a [I + 1])
{Temp = a [I];
A [I] = a [I + 1];
A [I + 1] = temp ;}
}
For (I = 1; I <11; I ++)
Printf ("% 5d,", a [I]);
Printf ("\ n ");
}

--------------
Bubble Algorithm
Algorithm Analysis and Improvement of Bubble Sorting
The basic idea of exchanging sorting is to compare the keywords of the records to be sorted in pairs. If the order of the two records is the opposite, the two records are exchanged until there is no reverse order record.
The basic concepts of application exchange sorting include Bubble sorting and quick sorting.

Bubble Sorting

1. Sorting Method
Vertically arrange the sorted record array R [1. n]. Each record R is considered as a bubble with the weight of R. key. According to the principle that a Light Bubble cannot be under a heavy bubble, scan the array R from the bottom up: Any Light Bubble scanned to a violation of this principle will make it "float" up ". This is repeated until the last two bubbles are light and heavy.
(1) initial
R [1. n] is an unordered area.

(2) First scan
The weights of two adjacent bubbles are compared from the bottom of the unordered area to the top. If the light bubbles are found to be in the lower and severe bubbles, the positions of the two bubbles are exchanged. That is, compare (R [n], R [n-1]), (R [n-1], R [N-2]),…, (R [2], R [1]); for each pair of bubbles (R [j + 1], R [j]), if R [j + 1]. key <R [j]. key, then the contents of R [j + 1] and R [j] are exchanged.
When the first scan is complete, the "lightest" bubble floated to the top of the interval, that is, the record with the smallest keyword is placed on the highest position R [1.

(3) second scan
Scan R [2. n]. When scanning is completed, the "light" bubble floated to the R [2] position ......
Finally, the sequential area R [1. n] can be obtained through n-1 scanning.
Note:
During the I-trip scan, R [1 .. I-1] and R [I.. n] are the current sequential and disordered areas, respectively. The scan continues from the bottom of the unordered area to the top of the area. When scanning is completed, the shortest bubbles in the area float to the top position R. The result is that R [1. I] is changed to a new ordered area.

2. Bubble sorting process example
Bubble Sorting of files whose keyword sequence is 49 38 65 97 76 13 27 49

3. Sorting Algorithm
(1) Analysis
Because each sort adds a bubble to the ordered area, there are n-1 bubbles in the ordered area after N-1 sort, in the disordered area, the bubble weight is always greater than or equal to the bubble weight in the ordered area. Therefore, the entire Bubble sorting process requires at most n-1 sorting.
If no bubble position exchange is found in a sorting, it means that all bubbles in the unordered area to be sorted meet the principle of being light and heavy. Therefore, the Bubble sorting process can be terminated after this sorting. Therefore, in the following algorithm, a Boolean exchange is introduced, which is set to FALSE before each sort starts. If an exchange occurs during the sorting process, set it to TRUE. Check exchange at the end of sorting. If exchange has not occurred, terminate the algorithm and no longer perform the next sorting.

(2) specific algorithms
Void BubbleSort (SeqList R)
{// R (l. n) is the file to be sorted. It uses bottom-up scanning to perform Bubble Sorting on R.
Int I, j;
Boolean exchange; // exchange flag
For (I = 1; I <G id = "1">

A simple program of C language Bubble Sorting

Main ()
{
Int I, j, temp;
Int a [10];
For (I = 0; I <10; I ++)
Scanf ("% d,", & a [I]);
For (j = 0; j <= 9; j ++)
{For (I = 0; I <10-j; I ++)
If (a [I]> a [I + 1])
{Temp = a [I];
A [I] = a [I + 1];
A [I + 1] = temp ;}
}
For (I = 1; I <11; I ++)
Printf ("% 5d,", a [I]);
Printf ("\ n ");
}

--------------
Bubble Algorithm
Algorithm Analysis and Improvement of Bubble Sorting
The basic idea of exchanging sorting is to compare the keywords of the records to be sorted in pairs. If the order of the two records is the opposite, the two records are exchanged until there is no reverse order record.
The basic concepts of application exchange sorting include Bubble sorting and quick sorting.

Bubble Sorting

1. Sorting Method
Vertically arrange the sorted record array R [1. n]. Each record R is considered as a bubble with the weight of R. key. According to the principle that a Light Bubble cannot be under a heavy bubble, scan the array R from the bottom up: Any Light Bubble scanned to a violation of this principle will make it "float" up ". This is repeated until the last two bubbles are light and heavy.
(1) initial
R [1. n] is an unordered area.

(2) First scan
The weights of two adjacent bubbles are compared from the bottom of the unordered area to the top. If the light bubbles are found to be in the lower and severe bubbles, the positions of the two bubbles are exchanged. That is, compare (R [n], R [n-1]), (R [n-1], R [N-2]),…, (R [2], R [1]); for each pair of bubbles (R [j + 1], R [j]), if R [j + 1]. key <R [j]. key, then the contents of R [j + 1] and R [j] are exchanged.
When the first scan is complete, the "lightest" bubble floated to the top of the interval, that is, the record with the smallest keyword is placed on the highest position R [1.

(3) second scan
Scan R [2. n]. When scanning is completed, the "light" bubble floated to the R [2] position ......
Finally, the sequential area R [1. n] can be obtained through n-1 scanning.
Note:
During the I-trip scan, R [1 .. I-1] and R [I.. n] are the current sequential and disordered areas, respectively. The scan continues from the bottom of the unordered area to the top of the area. When scanning is completed, the shortest bubbles in the area float to the top position R. The result is that R [1. I] is changed to a new ordered area.

2. Bubble sorting process example
Bubble Sorting of files whose keyword sequence is 49 38 65 97 76 13 27 49

3. Sorting Algorithm
(1) Analysis
Because each sort adds a bubble to the ordered area, there are n-1 bubbles in the ordered area after N-1 sort, in the disordered area, the bubble weight is always greater than or equal to the bubble weight in the ordered area. Therefore, the entire Bubble sorting process requires at most n-1 sorting.
If no bubble position exchange is found in a sorting, it means that all bubbles in the unordered area to be sorted meet the principle of being light and heavy. Therefore, the Bubble sorting process can be terminated after this sorting. Therefore, in the following algorithm, a Boolean exchange is introduced, which is set to FALSE before each sort starts. If an exchange occurs during the sorting process, set it to TRUE. Check exchange at the end of sorting. If exchange has not occurred, terminate the algorithm and no longer perform the next sorting.

(2) specific algorithms
Void BubbleSort (SeqList R)
{// R (l. n) is the file to be sorted. It uses bottom-up scanning to perform Bubble Sorting on R.
Int I, j;
Boolean exchange; // exchange flag
For (I = 1; I <G id = "1">