iOS Development Knowledge (v)

1. Process Control

• Sequential structure: The default process structure. Each statement is executed in the written order.

• Select structure: Judge a given condition and then decide which piece of code to execute based on the result of the decision.

• Loop structure: Executes a piece of code repeatedly when a given condition is true.

1. Select Structure-if

1. Simple to use

• An if (expression) statement 1;

• if (count>50) classes; Class

• An if (expression) statement 1; Else Statement 2;

• F (count>50) classes; else no classes;

• if (expression) {}

• if (count>50) {class, classroom;} else {}

• Scope of {}

• If-else If-else

• if (a==0) else if (a>0) Else

• Features: Only one parenthesis will be executed

• Compound condition

• The value range of class time (9~12 | | 14 ~17)

• Trap

• if (a!=0) {A is not 0;} else {A is 0;}

• if (a); {  }

• if (a=0)

• A = = 0;

• if (ten) int a = 9;

1. Exercises

2. Enter an integer day to represent the day of the week, output the corresponding day of the week according to the value of day, such as day==1, to output "Monday"

3. Enter an integer month to represent the month, according to the month output corresponding to the season.

Spring: 3, 4, 5

Summer: 6, 7, 8

Autumn: 9, 10, 11

Winter: 12, 1, 2

1. Enter an integer score to represent the score, based on the fractional output level (A-E) (in two ways)

a:90~100

b:80~89

c:70~79

d:60~69

E:0~60

1. Select Structure-switch

1. Simple to use

• switch (expression) {case numeric 1:break; ... default:break;}

• Example

int a = 10;

Switch (a) {

Case 0:

printf ("This is a 0");

Break

Case 5:

printf ("This is a 5");

Break

Case 10:

printf ("This is a 10");

Break

Default

printf ("nothing");

Break

}

• Briefly describe the role of break

• Defining variables in case

1. Comparison of IF and switch

• A lot of things are interchangeable.

• If used more, more flexible, switch can only a single value

1. Exercises

Use switch instead of if to implement the problem in if

1. Cyclic structure-while

1. Simple to use

• Continuous printf ("push-ups") 20 times;

• while (expression) {}

• Continue: Output 5 times take a break.

• Use of break: Stop a loop at a time

1. Characteristics

The loop body is executed only if the condition is established.

1. Exercises

2. Prompts the user to enter a positive integer n, computes the 1+2+3+...+n and

3. Prompts the user to enter a positive integer n, computes the 1-2+3-4+5-6+...+n and

4. Trap

while (condition);

1. Loop structure-do while

• Features: Must be executed once the body of the loop

• While and do While loop comparison

int i=0;
while (i<0) {
i++;
}

int i=0;
do{
i++;
} while (i<0);

1. Cyclic structure-for

1. Simple and practical

• Run process

• Initialization statements and so on can be multiple sentences (place printf in the for parentheses)

1. For loop nesting

Friends List 1

Friends 1

Friends 2

Friends List 2

Friends 1

Friends 2

Friends List 3

Friends 1

Friends 2

1. Trap

2. Dead loop for (;;);

3. Scope of internal variables for the for loop body

4. Scope obfuscation

for (int i = 0; i<5; i++) int a = 10;

1. Comparison of While loops and for loops

• Can be interchanged

• The variables for the for loop can be recovered in time

1. Exercises

2. Prompts the user to enter a positive integer n, if N5, outputs the following graph, other n values, and so on

1. Output 99 multiplication table

1. Break and Continue

1. Break

• Use occasion: switch\ cycle Structure

• Break under loop nesting

1. Continue

• Application: Cyclic structure

• Continue under cyclic nesting

iOS Development Knowledge (v)