catalogue
Definition of one-dimensional array
Initialization of one-dimensional array
Definition of two-dimensional array
Reference to two-dimensional array elements
Array description
- Array is one of the construction types
- An array is a collection of several variables with a certain order relationship. Each variable constituting the array is called the element of the array.
- The data types of elements in the array are required to be the same. It is determined by the array name and subscript. The array can be one-dimensional or multi-dimensional.
Definition of one-dimensional array
- The so-called one-dimensional array refers to an array with only one subscript, which is continuously stored in the memory of the computer.
- In C language, the general form of the name of one-dimensional array is as follows:
< storage type > < data type > < array name > [< expression >] for example: int a[6];- The array name represents the first address of memory. The address is always on, and sizeof (array name) is the memory space of the array.
Example:
#include<stdio.h>
int main (void)
{
int a[10];
int i ;
for(i = 0;i<10;i++)
printf("%p\n",&a[i]);
return 0;
}
Operation results:
0x7ffd148f8a20 0x7ffd148f8a24 0x7ffd148f8a28 0x7ffd148f8a2c 0x7ffd148f8a30 0x7ffd148f8a34 0x7ffd148f8a38 0x7ffd148f8a3c 0x7ffd148f8a40 0x7ffd148f8a44
-
Note: the program operation is the result obtained by running under linux system. The results obtained by everyone may be inconsistent.
%p is the format output controller for printing address information
Initialization of one-dimensional array
- Initialization method: assign initial values to array elements when defining an array
- int a[5] = {1,2,3,4,5};
- explain
- The array is not initialized and its element value is a random number
- If no initial value is assigned to the static array, the system will automatically assign a value of 0
- Only some array elements are given initial values
For Article 2:
static int a[5]; Equivalent to: a[0];a[1] = 0;a[2] = 0;a[3] = 0;a[4] = 0;
Example: the array only assigns initial values to some elements, and the remaining elements are replaced by 0
#include<stdio.h>
int main (void)
{
int a[10] = {1,5,6,8};//Array initialization partial elements
int i ;
for(i = 0;i<10;i++)
printf("%p，%d\n",&a[i],a[i]);//Print array values
return 0;
}
Operation results:
0x7ffc991407e0，1 0x7ffc991407e4，5 0x7ffc991407e8，6 0x7ffc991407ec，8 0x7ffc991407f0，0 0x7ffc991407f4，0 0x7ffc991407f8，0 0x7ffc991407fc，0 0x7ffc99140800，0 0x7ffc99140804，0
Definition of two-dimensional array
- Definition method: (when declaring, the number of columns cannot be omitted, and the number of rows can be omitted)
- Data type array name [constant expression] [constant expression]
For example:
int a[3][3]; float b[5][3];
- Storage order of array elements
- Two dimensional arrays are stored in row order first. Because the memory is one-dimensional, two-dimensional arrays need to be stored in order.
For example: int a[2][3]
| a[0][1] | a[0][2] | a[0][3] |
| a[1][1] | a[1][2] | a[1][3] |
Store a[0][1] before a[0][2]
Example:
#include<stdio.h>
int main(void)
{
int a[2][3];
int i,j;
for(i= 0;i<2;i++)
{
for(j = 0;j<3;j++)
printf("%p ",&a[i][j]);//Print array address
printf("\n");
}
/*Print number, address and array length*/
printf("%p %ld\n",a,sizeof(a));
/*Print the array address of the first line and the length of the data array*/
printf("%p %ld\n",a[0],sizeof(a[0]));
/*Print the array address of the second line and the length of the data array*/
printf("%p %ld\n",a[1],sizeof(a[1]));
return 0;
}
Operation results:
0x7fff263db870 0x7fff263db874 0x7fff263db878 0x7fff263db87c 0x7fff263db880 0x7fff263db884 0x7fff263db870 24 0x7fff263db870 12 0x7fff263db87c 12
Reference to two-dimensional array elements
- Form: array name [subscript] [subscript]
- Initialization of two-dimensional array elements
- Branch initialization
- Initialize in element order
Branch initialization
Example: int a [2] [3] = {1,2,3}, {4,5,6};
Initialize in element order
Example: int a[2][3]={1,2,3,4,5,6};
Multidimensional array
An array with two or more subscripts is called a multidimensional array.
Example: int a[2][3][4]// Is a three-dimensional array
Three dimensional arrays are rarely used in practical applications, so I won't introduce them here.
Character arrays and strings
Objectives:
- Master the usage of characters and numbers
- Master the usage of string
Character array
Character array is an array whose data type is character type, char c[10],ch[3][4];
Initialization of character array
- Assign char ch[5] = {'B','o','y'} character by character;
- Use the string constant char ch[6] = {"hello"};char ch[] = "hello";
Example:
#include<stdio.h>
int main()
{
int i,n,n1;
char ch[] = {'a','b','c'}; //character
char ch1[6] = {'a','b','c'};//String, the number of empty bits is represented by '\ 0'
n = sizeof(ch)/sizeof(char) //String length
for(i = 0;i < n;i++)
{
putchar(ch[i]);//Cyclic printing character
}
putchar('\n');
n1 = sizeof(ch)/sizeof(char) //String length
for(i = 0;i < n1;i++)
{
putchar(ch[i]);//Print string
}
putchar('\n');
return 0;
}
Operation results:
abc abc
character string
-
There is no string variable in C language. Use character array to process string
-
String end flag: '\ 0'.
For example, char str[] = "hello";
Indicates that the character length is 5 and ends with '\ 0'.
2D string array
Character array initialization
char fruit[][10] = {"apple","orange","pear","peach","banana"};
- Indicates that the two-dimensional array has 5 rows and 10 columns.
example
#include<stdio.h>
int main(void)
{
char fruit[][10] = {"apple","orange","pear","peach","banana"};
int i,k;
k = sizeof(fruit)/sizeof(fruit[0]);//Indicates how many lines there are
for(i = 0;i < k;i++)
{
printf("%s\n",fruit[i]);
}
return 0;
}
Operation results:
apple orange pear peach banana
Program example: string character reverse order
#include<stdio.h>
#include<string.h>
#define N 20
int main(void)
{
char arr[N] = {0};
char temp;
int i = 0,j,n,k;
printf("Plaese input a string!\n");
gets(arr);
n = strlen(arr);
j = n-1;
while(i<j)
{
temp = arr[i];
arr[i] = arr[j];
arr[j] = temp;
i++;
j--;
}
puts(arr);
return 0;
}
Operation results:
Plaese input a string! apple elppa