小朋友学C语言（29）：switch case语句

r囧r小猫 2022-06-05 23:57 207阅读 0赞

switch case语句与if elseif语句类似，都是从多个选择条件里选取一个来执行。

## （一）先来看一个if elseif程序 ##

#include <stdio.h>
    
    int main() 
    {
        int number;
        printf("Please input an integer between 1~7: ");
        scanf("%d", &number);
    
        printf("Today is ");
        if(1 == number) 
        {
            printf("Monday!");
        }
        else if(2 == number) 
        {
            printf("Tuesday!");
        }
        else if(3 == number) 
        {
            printf("Wednesday!");
        }
        else if(4 == number) 
        {
            printf("Thursday!");
        }
        else if(5 == number) 
        {
            printf("Friday!");
        }
        else if(6 == number) 
        {
            printf("Saturday!");
        }
        else if(7 == number) 
        {
            printf("Sunday!");
        }
        else
        {
            printf("a wrong day! Please input an integer between 1~7!");
        }
    
        return 0;
    }

运行结果：

Please input an integer between 1~7: 7
    Today is Sunday!

## （二）再用switch case语句实现相同的功能 ##

#include <stdio.h>
    
    int main() 
    {
        int number;
        printf("Please input an integer between 1~7: ");
        scanf("%d", &number);
    
        printf("Today is ");
        switch(number) 
        {
            case 1:
                {
                    printf("Monday!");
                    break;      
                }
            case 2:
                {
                    printf("Tuesday!");
                    break;      
                }
            case 3:
                {
                    printf("Wednesday!");
                    break;      
                }
            case 4:
                {
                    printf("Thursday!");
                    break;      
                }
            case 5:
                {
                    printf("Friday!");
                    break;      
                }
            case 6:
                {
                    printf("Saturday!");
                    break;      
                }
            case 7:
                {
                    printf("Sunday!");
                    break;      
                }
            default:
                {
                    printf("a wrong day! Please input an integer between 1~7!");
                    break;              
                }
        }
    
        return 0;
    }

运行结果1：

Please input an integer between 1~7: 7
    Today is Sunday!

运行结果2：

Please input an integer between 1~7: 10
    Today is a wrong day! Please input an integer between 1~7!

注意：  
switch case的结构为

switch(表达式或变量或常量)
    {
        case 条件1:
            {
                执行语句;
                break;
            }
        case 条件2:
            {
                执行语句;
                break;
            }
        ……
        default:
            {
                执行语句;
                break;
            }
    }

这里“break;”表示中断，若忘了写，程序会继续执行下面的条件。

## （三）试试下面这个程序 ##

#include <stdio.h>
    
    int main() 
    {
        int number;
        printf("Please input an integer between 1~7: ");
        scanf("%d", &number);
    
        printf("Today is ");
        switch(number) 
        {
            case 1:
                {
                    printf("Monday!");  
                }
            case 2:
                {
                    printf("Tuesday!");     
                }
            case 3:
                {
                    printf("Wednesday!");       
                }
            case 4:
                {
                    printf("Thursday!");    
                }
            case 5:
                {
                    printf("Friday!");      
                }
            case 6:
                {
                    printf("Saturday!");    
                }
            case 7:
                {
                    printf("Sunday!");      
                }
            default:
                {
                    printf("a wrong day! Please input an integer between 1~7!");           
                }
        }
    
        return 0;
    }

运行结果：

Please input an integer between 1~7: 3
    Today is Wednesday!Thursday!Friday!Saturday!Sunday!a wrong day! Please input an integer between 1~7!

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