[C language - zero foundation lesson 10] adventure of array Kingdom

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This issue is about the adventures of array Kingdom , If there is any mistake, please point out thank you ！

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Catalog

What is an array ？

One dimensional array

A reference to a one-dimensional array

Initialization of one dimensional array

A reference to a one-dimensional array

Two dimensional array

A reference to a two-dimensional array

Initialization of 2D array

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What is an array ？

I've been learning for such a long time C Have you ever thought about a question if I want to store each student's grade in a variable , How should we store data? Before we learn numbers, I believe we should set variables to store data . If there are 10 One student is using ten variables , It doesn't seem like much , It's not hard to define ten variables . If it is 1000 A student , You think the definition 1000 Is it hard for one variable ？ Of course it's hard . So we introduced an array that can store multiple same data types .

Array is to define a variable and set its length to store multiple data , Reference subscripts can be stored .

Arrays can be divided into One dimensional array and multi-dimensional array , And what we use most is One dimensional array and two dimensional array .

Be careful ： Array subscript from 0 Start

One dimensional array

The definition of one-dimensional array ：

One dimensional arrays are defined as ： Type specifier Array name 【 Constant expression 】;

 int arr[10];

Error model  

 int arr[10.5];

int a=10;
 int arr[a];

Be careful ：

1. Array definition , To specify the number of elements of the array , Constant expressions in square brackets are used to indicate the number of elements , That is, array length .
2. Constant expressions can include constants and symbolic constants , Can't contain variables .

A reference to a one-dimensional array

Array must be defined before using .C The language specifies that only array elements can be referenced one by one , You cannot reference the entire array at once .

The representation of array elements is ： Array name [ Subscript ]

int arr[]={0,1,2};
printf("%d\n",arr[1]);

  result 1

Initialization of one dimensional array

example 1：

int arr[3];
 arr[0]=0;
 arr[1]=1;
 arr[2]=2;

example 2：

int arr[4]={1,2};

example 3：

int arr[]={1,2,3};

A reference to a one-dimensional array

Find the smallest number in the array

#include<stdio.h>
int main(){
int arr[4]={6,5,1,0};
int max=arr[0];
for(int i=0;i<4;i++){
	if(max<arr[i]) 
	max=arr[i];
}
printf("%d\n",max);
}

Two dimensional array

The general form of the definition of a two-dimensional array is ：

Type specifier Array name [ Constant expression ][ Constant expression ]

int arr[3][3];

A reference to a two-dimensional array

Two dimensional array elements are represented as ： Array name [][]

With arr[3][3] As an example

We can quote

arr[0][0]  arr[0][1]  arr[0][2]

arr[1][0]  arr[1][2]  arr[1][2]

arr[2][0]  arr[2][2]  arr[2][2]

Initialization of 2D array

example 1：

	int arr[2][2]={
   {1,2},{2,2}};

arr[0][0] be equal to 1  arr[0][1] be equal to 2

arr[1][0] be equal to 2  arr[1][1] be equal to 2

example 2：

	int arr[2][2]={1,2,2,2};

arr[0][0] be equal to 1  arr[0][1] be equal to 2

arr[1][0] be equal to 2  arr[1][1] be equal to 2

example 3：

	int arr[2][2]={
   {1},{2}};

arr[0][0] be equal to 1  arr[0][1] be equal to 0

arr[1][0] be equal to 2  arr[1][1] be equal to 0

example 4：

int arr[][2]={1,2,3};

arr[0,0] be equal to 0   arr[1,1] be equal to 1

arr[1,0] be equal to 3   arr[1,1] be equal to 0

Be careful

Two dimensional arrays cannot omit row subscripts , But the column subscript cannot be omitted .

If there is no assignment, neither row nor column can be omitted

Arrays can be assigned fewer values, but not more

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