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
（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
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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