2022.1.23 diary

You cannot program with TAB key .

Relatively independent program blocks should be separated by one line .

In general , Valid comments for the source program must be in 20% above .

If there is any special abbreviation in the naming , There should be notes .

Add_User This form does not allow .

#define You cannot use numbers to name .

Function parameter order point ： During function call , Where the value of the variable changes （ spot ）, It is called a function parameter “ Order point ”.

A comma expression has a value .

Function parameters are evaluated from right to left .

atoi（a[i]）： Converts a numeric string to a numeric value .

va_list

Recursive function ： On function call , Calling one's own function directly or indirectly is called recursive function .

form ：

1. Call directly ------ Direct Recursion
2. Indirect invocation ------ Indirect recursion

 

  Recursive conditions ：

1. There must be a statement to complete the function task
2. A test to determine whether recursive calls can be avoided
3. A recursive call statement ; The parameters of this statement should gradually approach the end condition , So as to finally break the recursion
4. Test first , Post recursive call .

1、 A recursive call is not a recopy of the function , Every time it's called , New local variables and formal parameters will reallocate memory units in memory , And restart execution with a new variable ; Every recursive return , The local variables and formal parameters of the current calling layer are released , And return to the place where it was last called to continue execution ;

2、 Recursive calls generally do not save memory space , Because each call produces a new set of local variables , So as not to destroy the local variables of the upper layer ;

3、 Recursive calls generally do not speed up the execution of a program , Because each call must protect the upper local quantity ( The scene ), When returning, the upper local quantity must be restored , Take up execution time ;

4、 In recursive functions , There must be a condition to end recursion ;

5、 The advantage of recursive call is that it can solve some problems that are difficult to be solved by iterative algorithm .

1、 The creation of binary tree 、 Traverse 、 Balanced binary tree implementation code ;

2、 Hashtable

3、 Sorting method ： Dichotomy 、 Insertion method

Function to return pointer value ：

Format ： type * Function name （ Parameter list ）

* Function names cannot be surrounded by parentheses , Because parentheses have priority over * high . First a Combined with its subsequent parameters , indicate a Is the function name , Then with * combination , Indicates that it is a pointer function .

Int a[3][4];  a[i][j]

a : Indicates the starting address of the array name

i The address of ：a +i*l （l Is the byte length ）

a[0],a[1],a[2] Can be seen as a[3][4] The array name of a one-dimensional array of rows

  Enter the serial number to list the student's grades in four courses ：

 

A function pointer ： The function pointer is the physical entry address of the function . That is, at compile time , Assigned physical entry address .

（ Functions can be called through this pointer .）

Int(*p);

int max(int x,int y);

p=max;

take max There are three forms of the value of ：max(a,b);p(a,b);(*p)(a,b)

 

Function return pointer considerations ：

Local variable address cannot be returned .

solve ：

1、 Global variable address

2、 Dynamically allocate memory space

3、 Static local variables

Function definition considerations ：

1. Error return code
2. Check the entry parameters of function parameters
3. Control of function scale
4. Single function
5. Do not write functions that depend on other internal implementations
6. Function arguments don't have to be too many
7. Structure as function parameter , Try to use pointers

Write the function for all operations of string . Calling library functions... Is not allowed .

A pointer variable 8 Bytes .