Question

(1) Explain how a switch structure works, and discuss when to use a switch statement instead of an if…else statement.

Answer 1

`Hey,

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Switch case statement is used when we have multiple conditions and we need to perform different action based on the condition. When we have multiple conditions and we need to execute a block of statements when a particular condition is satisfied. In such case either we can use lengthy if..else-if statement or switch case. The problem with lengthy if..else-if is that it becomes complex when we have several conditions. The switch case is a clean and efficient method of handling such scenarios.

The syntax of Switch case statement:

switch (variable or an integer expression)
{
     case constant:
     //C++ code
     ;
     case constant:
     //C++ code
     ;
     default:
     //C++ code
     ;
}

Switch Case statement is mostly used with break statement even though the break statement is optional. We will first see an example without break statement and then we will discuss switch case with break

A switch statement is usually more efficient than a set of nested ifs. Deciding whether to use if-then-else statements or a switch statement is based on readability and the expression that the statement is testing.

1. Check the Testing Expression: An if-then-else statement can test expressions based on ranges of values or conditions, whereas a switch statement tests expressions based only on a single integer, enumerated value, or String object.
2. Switch better for Multi way branching: When compiler compiles a switch statement, it will inspect each of the case constants and create a “jump table” that it will use for selecting the path of execution depending on the value of the expression. Therefore, if we need to select among a large group of values, a switch statement will run much faster than the equivalent logic coded using a sequence of if-elses. The compiler can do this because it knows that the case constants are all the same type and simply must be compared for equality with the switch expression, while in case of if expressions, the compiler has no such knowledge.
3. if-else better for boolean values: If-else conditional branches are great for variable conditions that result into a boolean, whereas switch statements are great for fixed data values.
4. Speed: A switch statement might prove to be faster than ifs provided number of cases are good. If there are only few cases, it might not effect the speed in any case. Prefer switch if the number of cases are more than 5 otherwise, you may use if-else too.
   If a switch contains more than five items, it’s implemented using a lookup table or a hash list. This means that all items get the same access time, compared to a list of if:s where the last item takes much more time to reach as it has to evaluate every previous condition first.
5. Clarity in readability: A switch looks much cleaner when you have to combine cases. Ifs are quite vulnerable to errors too. Missing an else statement can land you up in havoc. Adding/removing labels is also easier with a switch and makes your code significantly easier to change and maintain.

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