Checking Keys

Part of the Logic & Flow section of Coddy's Kotlin journey. Lesson 4 of 63.

containsKey checks whether a key is present. containsValue searches values instead. Membership with key in map also checks keys. Keep these questions distinct when a key and a value have the same text.

Inside main:

val codes = mapOf("red" to "R")
println("R" in codes)

R is a value, not a key. The only key is red.

Use containsKey or in for keys; use containsValue for values.

Challenge

Medium

Complete keyExists with parameters stock: Map<String, Int>, key: String. Return whether key is present, including when its stored value is zero.

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 Boolean. 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 keyExists(stock: Map<String, Int>, key: String): Boolean {
    // Write your solution here.
    return false
}
fun main() {
    val stockCount = readln().toInt()
    val stock = mutableMapOf<String, Int>()
    for (i0 in 0 until stockCount) {
        val stockKey = readln()
        val stockValue = readln().toInt()
        stock[stockKey] = stockValue
    }
    val key = readLine().orEmpty()
    println(keyExists(stock, key))
}