Parsing Without Exceptions

Part of the Logic & Flow section of Coddy's Kotlin journey. Lesson 51 of 63.

toIntOrNull returns an Int for a valid in-range integer string and null when parsing fails, including overflow. Combine it with a safe branch or Elvis fallback. Trimming is a separate choice: explicitly trim if surrounding spaces should be accepted.

Inside main:

println(" 24 ".trim().toIntOrNull() ?: -1)

Trimming removes surrounding spaces before conversion succeeds.

toIntOrNull reports invalid or out-of-range integer text as null.

Challenge

Medium

Complete parseOrMissing with parameters text: String. Trim text and parse it as Int. Return -1 if parsing fails or the value is outside Int range.

Unless stricter bounds are stated above, collections contain at most 100 elements at each level, and integer arguments and integer collection values are between -1000 and 1000. Text supplied for parsing can include invalid or out-of-range representations as described.

Return a value of type Int. Keep the supplied input/output code. It reads scalar arguments one per line; a list starts with its count followed by its elements, and a map starts with its entry count followed by each key and value. Nested lists repeat the count-and-elements format for each row. The supplied main prints the return value followed by one newline. Lists use Kotlin's standard bracketed format; print no additional labels.

Try it yourself

fun parseOrMissing(text: String): Int {
    // Write your solution here.
    return 0
}
fun main() {
    val text = readLine().orEmpty()
    println(parseOrMissing(text))
}