In which of the following scenarios would you need to use a nested IF statement?

You use a nested if when the condition is dependent upon another condition. For example:

if (ptr != nullptr)

{

// ptr is non-null -- test the value it refers to

if (ptr* == 0)

{

// the value pointed to by ptr is zero

}

else

{

// the value pointed to by ptr is non-zero

}

}

In this case, the alternative to a nested if creates an inefficiency:

if (ptr != nullptr && *ptr == 0 )

{

// ptr is valid and refers to the value zero

}

else if (ptr != nullptr)

{

// ptr is valid and refers to a non-zero value

}

In this example, the expression "ptr != nullptr" is evaluated twice when ptr is valid and refers to a non-zero value. The nested if only evaluates this expression one time.