10-c language Arrays, strings

First, the basic concept of the array

A variable of type int can save a person's age, if you want to save the whole class age?

1. What is an array

An array, literally, is the meaning of a set of data, yes, an array is a set of data that is used to store

2. Features of the array

L can only hold one type of data, such as an array of type int, an array of type float

The data stored in the L is called "element"

Two, the definition of the array 1. Defined

L declaring the type of an array

L DECLARE the number of elements in an array (how much storage space is required)

2. Format

Element type array name [number of elements];

For example: int ages[3];

3. Simple to use

L Simple initialization: int ages[5] = {19, 19, 20, 21, 25};

L elements have sequential points, each element has a unique subscript (index), starting with 0

l access to array elements: A[i]

4. Initialization

L Initialization mode

u int a[3] = {10, 9, 6};

u int a[3] = {10,9};

u int a[] = {11, 7, 6};

u int a[4] = {[1]=11,[0] = 7};

L Common Errors

u int a[];

U int[4] A;

u int a[b];

U a = {10, 11};

U a[4] = {10,9,8,5};

5. Memory Analysis

L size of the array storage space

L Partition of storage space (memory allocation is from high address to low address, but an array interior element is from low to high)

L array name function, view element address

L array out of bounds attention

6. Other uses

L Array and function parameters

U array elements as function parameters

U array as function parameter (sizeof note)

L Traversing array elements

U Two Way traversal (while loop and for loop)

U traverse element value and element address

Use of the U-character array

7. Exercises

1> prompts for 5 students ' scores, calculates the average score, the highest score, the lowest score, and then outputs

2> Design a function: int arrayMax (int a[], int count) to find the maximum value of an array element

3> Design a function: int arraysum (int a[], int n), and the number of the first n of a one-dimensional array

4> design a function that stores elements in a one-dimensional integer array in reverse order. For example, it would have been 1,3,4,2, reverse storage has become: 2,4,3,1

Three or two-D array 1. What is a two-dimensional array

L An array can represent the age of a class, if you want to express a lot of classes?

L What is a two-dimensional array? int ages[3][10]; Three classes, 10 per class.

L equivalent to 3 rows and 10 columns

L equivalent of 3 one-dimensional arrays

The L two-dimensional array is a special one-dimensional array: its elements are one-dimensional arrays. For example, int a[2][3] can be thought of as consisting of a one-dimensional array a[0] and a one-dimensional array a[1], which all two one-dimensional arrays contain 3 elements of type int

2. Storage

L Storage Size

L Storage structure and order

L Storage Address issues

3. Initialization

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

l int A[3][4] = {{},{},{}};

L simple access to array elements

l int A[][5] = {3,21,31,2,32,1};

L NOTE the error:

int a[3][4];

A[3] = {};

4. Traverse

L Traverse all the elements

L Traverse Address

L Use occasions: Gobang, Tetris

Four, string 1. What is a string

L Simple string "itcast"

L One ' i ' is a character

L A lot of characters are grouped together as strings.

2. Initialization of strings

L char a[] = "123"; and char a [] = {' 1 ', ' 2 ', ' 3 '}, the difference can be compared size

L "123" is actually made up of ' 1 ', ' 2 ', ' 3 ', ' + '

• Storage distribution of "123"

L The output of the string "%s", ' \ n ' is not output

3. The role of the

L output char a[] = {' O ', ' K '};

L got "MJ" in front of Char a[].

L Output "MJ"

L re-output a

L Char a[] = {' I ', ' t ', ' + ', ' C '};

4. Commonly used string processing functions

L strlen (note Chinese)

5. Exercises

Write a function char_contains (char Str[],char c), if the string str contains the character C will return the value 1, otherwise return the value 0

V. Array of strings 1. Use Cases

* One-dimensional character array holds a string, such as a name char name[20] = "MJ"

* If you want to store multiple strings, such as the names of all students in a class, you need a two-dimensional character array, char names[15][20] can hold 15 students ' names (assuming the name does not exceed 20 characters)

* If you want to store two classes of student names, then you can use a three-dimensional character array Char names[2][15][20]

2. Initialization

Char Names[2][10] = {{' J ', ' a ', ' y ', ' \ n '}, {' J ', ' I ', ' m ', '/'}};

Char Names2[2][10] = {{"Jay"}, {"Jim"}};

Char names3[2][10] = {"Jay", "Jim"};

10-c language Arrays, strings