C++ switch statement

C++ Decision Making

In C++, the switch statement is used to execute different code blocks based on different conditions. It is often used to replace a series of if-else statements, making the code clearer and easier to read.

aswitchThe statement allows testing a variable for equality against multiple values. Each value is called a case, and the variable being tested is tested against eachswitch casePerform a check.

Syntax

In C++switchThe syntax of the statement:

switch(expression){ case constant-expression : statement(s); break; // Optional case constant-expression : statement(s); break; // Optional // You can have any number of case statements default : // Optional statement(s); }

switchThe statement must follow the rules below:

switchin the statementexpressionmust be an integer or enumeration type, or a class type that has a single conversion function converting it to an integer or enumeration type.
A switch can contain any number of case statements. Each case is followed by a value to compare and a colon.
of the caseconstant-expressionmust have the same data type as the variable in the switch, and must be a constant or a literal.
When the tested variable equals the constant in the case, the statements following the case will be executed until abreakuntil the statement.
When encounteringbreakstatement is encountered, the switch terminates, and control flow jumps to the next line after the switch statement.
Not every case needs to includebreak. If the case statement does not containbreak, the control flow willResumesubsequent cases, until a break is encountered.
aswitchThe statement can have an optionaldefaultcase, appearing at the end of the switch. The default case can be used to execute a task when none of the above cases are true. In the default casebreakThe statement is not required.

Flowchart

Example

#include <iostream>

int main() {
int day = 4;

switch (day) {
case 1:
std::cout << "Monday" << std::endl;
break;
case 2:
std::cout << "Tuesday" << std::endl;
break;
case 3:
std::cout << "Wednesday" << std::endl;
break;
case 4:
std::cout << "Thursday" << std::endl;
break;
case 5:
std::cout << "Friday" << std::endl;
break;
case 6:
std::cout << "Saturday" << std::endl;
break;
case 7:
std::cout << "Sunday" << std::endl;
break;
default:
std::cout << "Invalid day" << std::endl;
}

return 0;
}

When the above code is compiled and executed, it produces the following results:

Thursday

The char type in switch statements:

Example 2

#include <iostream> using namespace std; int main () { // Local variable declaration char grade = 'D'; switch(grade) { case 'A' : cout << "Great!" << endl; break; case 'B' : case 'C' : cout << "Well done" << endl; break; case 'D' : cout << "You passed" << endl; break; case 'F' : cout << "Better try again" << endl; break; default : cout << "Invalid score" << endl; } cout << "Your score is" << grade << endl; return 0; }

When the above code is compiled and executed, it produces the following results:

您通过了
您的成绩是 D

Notes:

breakStatement:eachcaseat the end of the statementbreakThe statement is necessary to break out ofswitchstatement. If missingbreak, the program will continue to execute the nextcase, this is called "fall-through".
defaultStatement: defaultThe statement is optional, but usually in allcasewhen none of them match, it is used to handle all unlisted cases.
Expression type: switchThe expression is usually an integer or enumeration type; floating-point and string types are not feasible.

Sometimes we may intentionally use fall-through. In the following code, if number is 2 or 3, the same code block will be executed.

Example

#include <iostream>

int main() {
int number = 2;

switch (number) {
case 1:
std::cout << "Number is 1" << std::endl;
break;
case 2:
case 3:
std::cout << "Number is 2 or 3" << std::endl;
break;
default:
std::cout << "Number is not 1, 2, or 3" << std::endl;
}

return 0;
}

When the above code is compiled and executed, it produces the following results:

Number is 2 or 3

C++ Decision Making

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