C Basic grammar--arrays

One or one-D arrays

1. What is an array

2. Array syntax

3. Subscript

4. Initialization

5. Array name and the first address of the group

Application of two or one-D array

1. Assignment and copying of arrays

2. Positive and negative traversal of arrays

3. Random number

4. Array Chaos sequence

5, the repetition of the array

Three or two-D arrays

1, array of arrays

2. Initialization of two-dimensional arrays

3. Array names for two-dimensional arrays

Application of four or two-D array

1, two-dimensional array and two-dimensional table

2. Subscript Calculation

One or one-D arrays

1. What is an array

? An array is a data structure used to store multiple identical data types. Container

Analyze key points:

-Multiple strips
-Same type

-the array is the container for the data, not the data itself
-Each data in an array, called an element, consists of multiple elements (data). -Data Subscript (index) to differentiate elements in the data
-the element starts at position 0 of the array

-Elements can use the array variable name [subscript] to get concrete elements-the number of elements in the array is called the length of the array
-Space occupied by the array = type of element * Array length
-Array is a contiguous area of memory pointer
-array variable points to the area, is the array in memory of the first address

2. Array syntax

? Define array: Element type array name [number of elements];

int array[3];

? Access element: array name [subscript]

Array[0] = 10;

3. Subscript

? Subscript refers to the number in brackets when an array element is accessed

? The subscript cannot be crossed out, and if it is out of bounds, the following consequences may result:

– Program crashes directly
– Momin changes the values of other variables or data spaces
– Nothing happened.

4. Initialization

? Value assigned to use

int array2[3]={3,4,5};//assigns values to array elements in turn
int array4[3]={1,2};//If the number of assignments is less than the length of the array, the following values are automatically populated with zeros

? Assign 0 value

int array[3];//is not initialized when there may be garbage

Each element in an int array3[3]={0};//array is 0

5. Array name and the first address of the group

? The array name is an address, and it is an immutable address

? The array name cannot be an lvalue, or it cannot appear to the left of an assignment statement. Except for initialization.

? The array name is a constant (pointer). So you can't assign a value

Application of two or one-D array

1. Assignment and copying of arrays

? assigning values to arrays

int array[10];
ARRAY[2] = 10;//assigns the third element of the array to a value of 10

? Copy of array

int array[10] = {1,2,3,4,5,6,7,8,9,0};

int num [10];
for (int i = 0; i <; i++)

Num[i] = Array[i];

2. Positive and negative traversal of arrays

? Forward traversal of arrays

int array[10] = {1,2,3,4,5,6,7,8,9,0};

for (int i = 0; i <; i++)

printf ("%d", array[i]);

? Inverse traversal of an array

for (int i = 9; I >= 0; i--)

printf ("%d", array[i]);

3. Random number

? The rand () function is used to generate a random number

? The Srand () function is used to define random seeds

int main () {

Srand ((unsigned) time (0));

for (int i=0; i<10; i++) {

int x = rand ()% 100;

}

printf ("%d", x);

printf ("\ n");

return 0;

}

4. Array Chaos sequence

? Array shuffle refers to the random arrangement of elements in an array

int main () {

int array[10] = {1,2,3,4,5,6,7,8,9,0};

Srand ((unsigned) time (0));
for (int i=0; i<10; i++) {

int x = rand ()% (10-i) + i;

int temp = Array[i];
Array[i] = array[x];

}

ARRAY[X] = temp;

for (int i=0; i<10; i++)

printf ("%d", array[i]);

return 0;

}

5, the repetition of the array

? The repetition of an array element refers to the existence of the same array element in the array

Three or two-D arrays

1, array of arrays

? Define array: Element type array name [number of elements] [number of elements];

int array[3][4];

? Access element: array name [subscript] [subscript]

ARRAY[1][2] = 10;

2. Initialization of two-dimensional arrays

? corresponding element content

int array2[3][2]={{1,2},{3,4},{5,6}};

? Overall assignment

int array2[3][2]={1,2,3,4,5,6};

? Assign value auto-complement 0

int array2[3][2]={1,2,3,4};

3. Array names for two-dimensional arrays

? The two-dimensional array name is also an address, and it is an immutable address

? Two-dimensional array names are also not allowed to be left, or to the left of an assignment statement. Except for initialization.

? A two-dimensional array name is a constant (pointer). So you can't assign a value

Application of four or two-D array

1, two-dimensional array and two-dimensional table

? A two-dimensional array is actually an array of arrays
? A two-dimensional array can be understood as a two-dimensional table with several rows and columns.

2. Subscript Calculation

? The storage method of two-dimensional array in memory is to store the column and then save the release.

Eg:int Array[3][4];

The order in which the memory is stored is:

ARRAY[0][0]

ARRAY[0][1]

ARRAY[0][2]

ARRAY[0][3]

ARRAY[1][0]

ARRAY[1][1]

ARRAY[1][2]

ARRAY[1][3]

ARRAY[2][0]

ARRAY[2][1]

ARRAY[2][2]

ARRAY[2][3]

C Basic grammar--arrays