Range operators (... and ..<) in Swift - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of inclusive range loop

What is the output of this Swift code using the inclusive range operator ...?

Swift

for i in 1...3 {
    print(i, terminator: ",")
}

A 2,3,4,

B 1,2,

C 1,2,3,4,

D 1,2,3,

💡 Hint

Inclusive range includes both start and end values.

The ... operator creates a range that includes both the start and the end values. So the loop runs for 1, 2, and 3.

❓ Predict Output

intermediate

Output of half-open range loop

What is the output of this Swift code using the half-open range operator ..<?

Swift

for i in 1..<4 {
    print(i, terminator: "-")
}

A 1-2-3-

B 1-2-3-4-

C 2-3-4-

D 1-2-

💡 Hint

Half-open range excludes the end value.

The ..< operator creates a range that includes the start but excludes the end. So the loop runs for 1, 2, and 3.

🔧 Debug

advanced

Why does this range cause a runtime error?

Consider this Swift code snippet:

let numbers = [10, 20, 30]
for i in 0...numbers.count {
    print(numbers[i])
}

What error will this code cause when run?

A No error, prints all elements

B Index out of range runtime error

C Syntax error: missing colon

D Type error: cannot subscript array with Int

💡 Hint

Check the range bounds against the array indices.

The 0...numbers.count range includes the value 3, but the array indices go from 0 to 2. Accessing numbers[3] causes an index out of range error.

🧠 Conceptual

advanced

Count of elements in a half-open range

How many elements are in the range 5..<10 in Swift?

A 5

B 6

C 4

D 10

💡 Hint

Count is end minus start for half-open ranges.

The half-open range 5..<10 includes 5,6,7,8,9 which is 5 elements.

🚀 Application

expert

Using range operators to slice arrays

Given let arr = ["a", "b", "c", "d", "e"], which option correctly extracts the subarray ["b", "c", "d"] using range operators?

A arr[0..<3]

B arr[1...3]

C arr[1..<4]

D arr[2...4]

💡 Hint

Remember that array indices start at 0 and half-open ranges exclude the upper bound.

The subarray ["b", "c", "d"] corresponds to indices 1, 2, and 3. The half-open range 1..<4 includes 1, 2, and 3.