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How to analyze the choice structure of C language, I believe that many inexperienced people do not know what to do about it. Therefore, this paper summarizes the causes and solutions of the problem. Through this article, I hope you can solve this problem.

1. If-else statement 1. Single selection

You can simply select the if statement. The syntax and execution flow of the if statement are as follows:

If (expression) {code block (executed when the expression returns true)}

When the program runs to the if statement, it will be judged by the expression. If the return value of the no expression is true, it will enter the code block to execute the statement, and if it is false, skip the code block to continue execution. (curly braces can be omitted when there is only one sentence in a contemporary code block statement. )

Give me a simple example.

Example: judge whether 10 is a multiple of 3

Int main () {int I = 10; if (I% 3 = = 0) / / the expression result is false printf ("yes"); / / return 0 is not executed within the code block;} 2. Double selection

Double selection is achieved through the if-else statement. The syntax and execution flow of the if-else statement are as follows:

(else match: else matches the nearest if from which it is located)

If (expression) {statement one (execute when expression returns true)} else {statement two (executed when expression return value is false)}

When the program runs to the if statement, it is determined by the expression, and if the return value of the expression is true, statement 1 is executed and statement 2 is executed for the fake stool block.

Give me a simple example.

Ex.: judge the students to pass the score

# includeint main () {int I = 0; scanf ("% d", & I); if (I > = 60) printf ("pass"); else printf ("fail"); return 0;} 3. Multiple choice

The syntax and execution flow of the else if statement are as follows:

If (expression 1) {statement 1 (execution when expression 1 returns true)} else if (expression 2) {statement 2 (execution when expression return value is true)} else if (expression 3) {statement 3 (execution when expression return value is true)} else {code block (execution when all above expressions are false)}

When the program runs to the if statement, it will be judged by the expression. If the return value of expression 1 is true, then enter the code block under if to execute statement 1, and enter expression 2 if it is false. Of course, if-else can achieve more than these four branches, by increasing the number of else if statements can achieve more choices.

Give me a simple example.

Example: age segment

# include int main () {int age = 0; scanf ("% d", & age); if (age

< 18) { printf("少年\n"); } else if (age >

= 18 & & age

< 30) { printf("青年\n"); } else if (age >

= 30 & & age

< 50) { printf("中年\n"); } else if (age >

= 50 & & age

< 80) { printf("老年\n"); } else { printf("老寿星\n"); } return 0;}二.switch语句 switch语句也是一种分支语句。 常常用于多分支的情况。else if 语句也能实现多分支情况，但在某些情况下使用else if来实现，会使代码过于复杂。 比如： 输入1，输出星期一 输入2，输出星期二 输入3，输出星期三 输入4，输出星期四 输入5，输出星期五 输入6，输出星期六 输入7，输出星期日 如果使用else if #includeint main(){ int day = 0; scanf("%d", &day); if (1 == day) printf("星期一"); else if (2 == day) printf("星期二"); else if (3 == day) printf("星期三"); else if (4 == day) printf("星期四"); else if (5 == day) printf("星期五"); else if (6 == day) printf("星期六"); else printf("星期日"); return 0;} 那么这个代码便会太过复杂，而使用switch就会很多 switch语句的语法及执行流程如下： switch(整型表达式){ //在一个 switch 中可以有任意数量的 case 语句。 case 整形常量表达式: 语句;} case 是一个入口，按照输入整型表达式的值进入，后按照顺序依次运行。 单使用switch语句是无法实现分支的，需要搭配break使用才能实现真正的分支。 举一个例子： #include int main(){ int day = 0; scanf("%d", &day); switch (day) { case 1: printf("星期一\n"); case 2: printf("星期二\n"); case 3: printf("星期三\n"); case 4: printf("星期四\n"); case 5: printf("星期五\n"); case 6: printf("星期六\n"); case 7: printf("星期天\n"); } return 0;} 输入值分别为2 4时，输出结果如下：

It's a far cry from what you want to achieve, and using it with break can solve this problem.

# include int main () {int day = 0; scanf ("% d", & day); switch (day) {case 1: printf ("Monday\ n"); break; case 2: printf ("Tuesday\ n"); break; case 3: printf ("Wednesday\ n"); break Case 4: printf ("Thursday\ n"); break; case 5: printf ("Friday\ n"); break; case 6: printf ("Saturday\ n"); break; case 7: printf ("Sunday\ n"); break;} return 0;}

The actual effect of the break statement is to divide the list of statements into different branches.

Switch is often used with default statements as well as with break statements.

If the expressed value does not match the values of all case tags, all statements will be skipped. The program does not terminate and does not report an error, because this situation is not considered an error in C.

You can add a default clause to the list of statements when you don't want to ignore the values of expressions that don't match all tags.

When the value of the switch expression does not match the values of all case tags, the statement following the default clause is executed.

For example:

# include int main () {int day = 0; scanf ("% d", & day); switch (day) {case 1: printf ("Monday\ n"); break; case 2: printf ("Tuesday\ n"); break; case 3: printf ("Wednesday\ n"); break Case 4: printf ("Thursday\ n"); break; case 5: printf ("Friday\ n"); break; case 6: printf ("Saturday\ n"); break; case 7: printf ("Sunday\ n"); break; default: printf ("typing error");} return 0;}

The switch statement can have an optional default case that appears at the end of the switch. Default case can be used to perform a task when none of the above case is true. The break statement in default case is not required.

What is C language? C language is a process-oriented and abstract general programming language, which is widely used in low-level development. C language can be used to compile and process low-level memory in a simple way.

After reading the above, have you mastered the method of how to analyze the selective structure of C language? If you want to learn more skills or want to know more about it, you are welcome to follow the industry information channel, thank you for reading!

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