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Indexes ：

1. One dimensional array

2. Two dimensional array

One dimensional array

1.  Array creation

    stay csdn Typing this kind of code is too monotonous Bloggers upload screenshots  

  It is not difficult to find through debugging , The other numbers in the array are 0. therefore , We can do this when creating arrays , When I didn't know what to initialize at first , Direct initialization 0, Such as this ：int  arr[143] = {0}, In the later stage, you can change the use to the corresponding variable , Because if you don't initialize , Just one int arr[143]; So there are random values in the array , If you are uncertain, your code is prone to unpredictable errors , So we should form a good habit

3. Use of arrays ：

Let's give you an example ：

int arr[5] = {1,2,3,4,5}

But their subscript is 0,1,2,3,4

 4. Calculate the size of the array

Sometimes you can calculate the size of an array with strlen  It can also be used. sizeof Calculation

Blogger here to elaborate again strlen And sizeof The difference between!

strlen It's actually a function library , It can only measure the length of the string , And only for strings , The purpose is to see if there is... In the string “\0” And then I'll talk about \0 The size of the front is measured

sizeof： The essence is an operator （ Operator ）, It is used to calculate the space occupied by variable memory , Any type can be used , Don't pay attention to whether there is \0, Speaking of this , Or some code , Better understanding ！

  because “zjt” In fact, in the computer, it means { ‘z’,‘j’,‘t’,‘\0’};

Use strlen and sizeof test dy2 The length will be different

Then note that you are using strlen When you need to add a header file <string.h>

I almost forgot ！

There is another way to measure the size of the array

int arr[10] = {1,23,4,5};
int sz = sizeof(arr)/sizeof(arr[0]);

So you will ？

Then you can use sizeof This function    int arr[10] = {1,2,3,4,5};

Find out what will happen

You must think it's 10 Or 5

It's not

40 = 10*4;

10： Indicates that the space opened up by this array is 10

4： The space occupied by an integer is four bytes

The reason why the last example is so clever is because char The space occupied by the character type itself is a byte

So if not char Type array

 int sz = sizeof(arr)/sizeof(arr[0]); We use this

yes char Type words , Can directly

int sz = sizeof(arr)：

5. One dimensional array storage

Learn how arrays are stored , Lay the foundation for future operation and use

eg：

  Then we use a for Loop and print out the address to see

Explain What you need to print the address is %p;

 

  We can see that the address of the previous string differs by four bytes , The difference between each address of the following string is 1 Bytes , Look ahead , One is int One is char It should be understandable .

And what I want to explain is that arrays are stored continuously in memory , This is very helpful for us to do questions .

Talked about before     If ：int*p = &a;

                            So actually p Namely a The address of , also *p  = a;

And now we know that arrays are stored continuously in memory

We can also print the address through the dereference operator

 

  We can see As like as two peas       It is proved once again that arrays are stored continuously in memory .

2. Two dimensional array

One dimensional array is done , Now we come to the two-dimensional array

Actually, I think it's just as good as math , Two dimensional array , Just like the coordinates of Mathematics

The horizontal and vertical coordinates are the same   The two-dimensional array is roughly as follows

 

  Initialization of 2D array

eg：int arr[2][3] = {1,2,3,4,5,6};

Someone wants to ask , The size of an array in a one-dimensional array can be omitted directly , What about two-dimensional arrays ？

Before that, popularizing one was just 【x】【y】; Let's assume that these are the two numbers behind the two-dimensional array that represent the size of the array ,

that x Said line ,y The column , And we can omit rows but not columns when initializing a two-dimensional array

So let's go through Storage of two-dimensional arrays To illustrate , Through the first vs2019 Take a look at the debugging of

  We can see that the arrangement of two-dimensional arrays is similar to what we think , But rough storage ？？

  It is found that the storage of two-dimensional arrays is similar to that of one-dimensional arrays

therefore

 

In fact, two-dimensional arrays should be arranged like this , According to the array we set , Two lines in all , Three columns in one row , So I drew it in the picture , If you omit Columns , How should arrays be stored in space ？ conversely , If you omit the line , The array only needs to know when to start a new line , Until it is completely stored .