C Tutorial/Statement/Switch statement
Содержание
- 1 break statement stops evaluating any further case statements.
- 2 Confused if statement
- 3 In the absence of a break statement, all statements that are followed by matched cases are executed.
- 4 Nest if statement in case statement
- 5 The switch statement
- 6 Two cases, one action
- 7 Use switch structure to evaluate characters
- 8 Use switch to simplify the logic
- 9 Use the switch structure to evaluate a user"s response from a menu (without break).
break statement stops evaluating any further case statements.
#include <stdio.h>
main(){
int iResponse = 0;
printf("\nPlease select a category (1-4): ");
scanf("%d", &iResponse);
switch (iResponse) {
case 1:
printf("\nYou selected 1\n");
break;
case 2:
printf("You selected 2\n");
break;
case 3:
printf("You selected 3\n");
break;
case 4:
printf("You selected 4\n");
break;
}
}Please select a category (1-4): 2
You selected 2
Confused if statement
#include <stdio.h>
#include <stdbool.h>
int main(void)
{
int age = 24;
int college = 1;
int subject = 2;
bool interview = false;
if((age>25 && subject==1) && (college==3 || college==1))
interview = true;
if(college==2 &&subject ==1)
interview = true;
if(college==1 && subject==2 && !(age>28))
interview = true;
if(college==2 && (subject==2 || subject==3) && age>25)
interview = true;
if(interview)
printf("\n\nGive "em an interview");
else
printf("\n\nReject "em");
return 0;
}Give "em an interview
In the absence of a break statement, all statements that are followed by matched cases are executed.
#include <stdio.h>
main(){
int i= 6;
switch(i%2)
{
case 0 : printf("the number %d is even \n",i);
case 1 : printf("the number %d is odd \n",i);
break;
}
}the number 1 is odd
the number 2 is even
the number 3 is odd
the number 4 is even
Nest if statement in case statement
#include <stdio.h>
#include <ctype.h>
int main(void)
{
double number1 = 3.0;
double number2 = 4.0;
char operation = "+";
char reply = 0;
switch(operation)
{
case "+":
printf("= %lf\n", number1 + number2);
break;
case "-":
printf("= %lf\n", number1 - number2);
break;
case "*":
printf("= %lf\n", number1 * number2);
break;
case "/":
if(number2 == 0)
printf("\n\n\aDivision by zero error!\n");
else
printf("= %lf\n", number1 / number2);
break;
case "%":
if((long)number2 == 0)
printf("\n\n\aDivision by zero error!\n");
else
printf("= %ld\n", (long)number1 % (long)number2);
break;
default:
printf("\n\n\aIllegal operation!\n");
break;
}
return 0;
}= 7.000000
The switch statement
To take one of a number of possible actions.
switch is preferred over multiple if...else statements.
The general form of a switch statement is
switch(switch_expr)
{
case constant expr1 : S1;
S2;
break;
case constant expr1 : S3;
S4;
break;
.....
default : S5;
S6;
break;
}Two cases, one action
#include <stdio.h>
int main(void)
{
char answer = 0;
printf("Enter Y or N: ");
scanf(" %c", &answer);
switch (answer)
{
case "y": case "Y":
printf("\nYou responded in the affirmative.");
break;
case "n": case "N":
printf("\nYou responded in the negative.");
break;
default:
printf("\nYou did not respond correctly...");
break;
}
return 0;
}Enter Y or N: N
You responded in the negative.
Use switch structure to evaluate characters
#include <stdio.h>
main(){
char iResponse = "A";
printf("input(a or A or B or b or c or C):");
scanf("%d", &iResponse);
switch (iResponse) {
case "a": case "A":
printf ("\nYou selected the character a or A\n");
break;
case "b": case "B":
printf("You selected the character b or B\n");
break;
case "c": case "C":
printf("You selected the character c or C\n");
break;
}
}Use switch to simplify the logic
#include <stdio.h>
int main(void)
{
int choice = 2;
if((choice>10) || (choice <1)){
choice = 11;
}
switch(choice)
{
case 7:
printf("\nCongratulations!");
break;
case 2:
printf("\nA");
break;
case 8:
printf("\nB");
break;
case 11:
printf("\nC");
default:
printf("\nSorry, you lose.\n");
break;
}
return 0;
}A
#include <stdio.h>
main(){
int iResponse = 0;
printf("\nPlease select a category (1-4): ");
scanf("%d", &iResponse);
switch (iResponse) {
case 1:
printf("\nYou selected 1\n");
case 2:
printf("You selected 2\n");
case 3:
printf("You selected 3\n");
case 4:
printf("You selected 4\n");
} //end switch
} //end main functionPlease select a category (1-4): 1
You selected 1
You selected 2
You selected 3
You selected 4
