switch statement

The switch statement is used to select one of many code blocks to be executed. Very similar to if-else statements.

I don’t use these much.

Example

int a = 5;
 
switch(a) {
    case 1:
        ...
        break;
 
    case 2:
        ...
        break;
 
    case 3:
        ...
        break;
    default:
        ...
        break;
}

What is the default keyword?

The default keyword specifies some code to run if there is no case match

BE CAREFUL, if you forget the break, then the statement will continue running.

For example,

switch (1) {
    case 1:
        std::cout << '1'; // prints "1",
    case 2:
        std::cout << '2'; // then prints "2"
}

When should you use switch over if ... else?

If a switch contains more than five items, it’s implemented using a lookup table or a hash list.

Therefore, if you are comparing against constant values, the switch syntax is likely preferable, since you can compare in $O(1)$ time rather than in $O(n)$ time for an if...else statement.