Deep understanding of array related problems in C language

    Hello, everyone ！ I'm Xiao Yang . Xiao Yang Ba C The common problems in arrays in language are summarized , I hope I can help you while facilitating your understanding and review .

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  List of questions ：

problem 1： The difference between the two ways of writing character arrays ？

problem 2： Can a two-dimensional array be regarded as a one-dimensional array ?

problem 3： The storage relationship between one-dimensional array and two-dimensional array in memory ？

problem 4： The number of rows of a two-dimensional array can be omitted , The reason why the number of columns cannot be omitted ？

problem 5： One dimensional array and two-dimensional array cross-border access ？

problem 6： Array parameter transfer , Two ways of writing formal parameters ？

problem 7： Bubble sort to sort integer arrays in ascending order ？

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Problem solving ：

problem 1： Two ways to write character arrays ？

answer ： because C There is no string type in the language , So use char Array instead of string type , There are two ways to define character arrays , Respectively ： In single character form and string form .
Mode one ： In single character form
To declare initialization of a character array that can store four valid values , Form the following ：
char ch[4]={'w','o','r,'d'};

Mode two ： In string form
To declare initialization of a character array that can store four valid values , Form the following ：
char str[5]=''word";// The size of string array must be declared as 5, Because we should set aside str[4] Automatically store for the compiler '\0', If the declaration is initialized to ：char str[4]="word", Report errors

Be careful ：
1. When it is not full , For two arrays , The remaining valid positions are initialized as '\0' 
2. When it's full , The last valid position of the character array is not necessarily assigned '\0', It can still be a valid value you want to store , But the last valid position of the string array must be '\0'

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problem 2： Can a two-dimensional array be regarded as a one-dimensional array ?

answer ： Sure , The two-dimensional array is originally regarded as a special one-dimensional array , It can be understood that a two-dimensional array is an array of one-dimensional arrays . Popular understanding is ： Each row of the original two-dimensional array represents the elements in the special one-dimensional array .

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problem 3： The storage relationship between one-dimensional array and two-dimensional array in memory ？

answer ： The layout of one-dimensional array and two-dimensional array in memory is the same , That is, it is stored continuously in memory , Move from low address to high address ; However, there are some differences between the two forms of access , They are accessed in the form of one-dimensional array and two-dimensional array .

Schematic diagram of one-dimensional array storage in memory ：

Schematic diagram of two-dimensional array storage in memory ：

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problem 4： The number of rows of a two-dimensional array can be omitted , The reason why the number of columns cannot be omitted ？

answer ： Two dimensional arrays can omit rows . Because two-dimensional arrays are stored “ First, then ”, If you do not specify the number of columns , You can't know how many data to put in a row , As long as you know the number of columns , The platoon leader can know how many lines can be put in total . 

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problem 5： One dimensional array and two-dimensional array cross-border access ？

answer ： The subscript of an array is range limited . The next stipulation of the array is from 0 At the beginning , If the array has n Elements , The subscript of the last element is n-1. So if the subscript of the array is less than 0, Or greater than n-1, The array is accessed out of bounds , Access beyond the legal space of the array . Rows and columns of two-dimensional arrays may also be out of bounds . and C The language itself does not check the bounds of array subscripts , The compiler does not necessarily report an error , But the compiler does not report an error , That doesn't mean the program is That's right. , So when programmers write code , You'd better do cross-border inspection yourself .

One dimensional array out of bounds diagram ：

Schematic diagram of two-dimensional array out of bounds ：

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problem 6： Array parameter transfer , Two ways of writing formal parameters ？（ And problems 7 Related to ）

answer ： How to write it 1： Array form     How to write it 2： Pointer form

Sample questions 7 To specify both .

Schematic diagram of array form ：

Schematic diagram of pointer form ：

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problem 7： Bubble sort to sort integer arrays in ascending order ？

answer ： Bubble sorting core idea ： Compare two adjacent elements .

The result of bubble sort is that a bubble sort brings a data to its final position .

Schematic diagram of bubble sorting principle ：

Schematic diagram of the first bubble sorting process ：

  Flow diagram of sequential bubble sorting ： 

Code examples and partial analysis ：

  Code output result diagram ：

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Conclusion

friends , When you learn here , You should have harvested a lot ！🥳🥳🥳 Xiao Yang will summarize other contents for you later , Constantly update high-quality content to help you , Progress together . come on. , Dream catcher ! Let's embrace a better tomorrow !

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