Expected

Use Integer.MAX_VALUE in order to consistently return a large number for the purposes of comparison.

Observed

Integer.MAX_VALUE is returning a negative number.

Implement

In the sample code values are saved into a 2D table in order to find the minimum amount of coins required to make up a given amount.

Using Integer.MAX_VALUE

-2147483647 is being derived from Integer.MAX_VALUE.

fun main() {
// Steps - Iterative/bottom-up
//     1. Create a 2D table: Rows = Denominations(Denoms), Columns = Amount(Amt)
//     2. Store min # of coins in at [R][C] = Min(currentDenomMin, previousDenomMin)
//         a. currentDenomMin = [R][C - coins.get(R)] + 1
//         b. previousDenomMin = [R - 1][C]
//     3. Return minCount or -1 for table[coins.size - 1, Amt].
    println("Min count: ${coinChange(intArrayOf(2), 3)}")
}

lateinit var table: Array<IntArray>
lateinit var mCoins: IntArray
private val maxValue = Integer.MAX_VALUE
fun coinChange(coins: IntArray, amt: Int): Int {
    table = Array(coins.size, { IntArray(amt + 1) })
    mCoins = coins
    coins.sort()
    buildMinCounts(amt)
    val minCount = table[coins.size - 1][amt]
    return if (minCount == maxValue) -1 else minCount

}

fun buildMinCounts(amt: Int) {
    for (r in 0..mCoins.size - 1) {
        for (c in 0..amt) {
            val currentDenomValue = mCoins.get(r)
            val currentDenomMin = getDenomMin(r, c - currentDenomValue) + 1
            val previousDenomMin = getDenomMin(r - 1, c)
            if (c == 0) {
                table[r][c] = 0
            } else table[r][c] = Math.min(currentDenomMin, previousDenomMin)
        }
    }
}

fun getDenomMin(r: Int, c: Int): Int {
    if (r < 0 || c < 0) return maxValue
    else return table[r][c]
}

fun printT(amt: Int) {
    for (r in 0..mCoins.size - 1) {
        for (c in 0..amt) {
            print("${table[r][c]} ")
        }
        println("")
    }
}

Using 999999999 as the maxValue instead

Works as expected.

fun main() {
    println("Min count: ${coinChange(intArrayOf(2), 3)}")
}

lateinit var table: Array<IntArray>
lateinit var mCoins: IntArray
private val maxValue = 999999999
fun coinChange(coins: IntArray, amt: Int): Int {
    table = Array(coins.size, { IntArray(amt + 1) })
    mCoins = coins
    coins.sort()
    buildMinCounts(amt)
    val minCount = table[coins.size - 1][amt]
    return if (minCount == maxValue) -1 else minCount

}

fun buildMinCounts(amt: Int) {
    for (r in 0..mCoins.size - 1) {
        for (c in 0..amt) {
            val currentDenomValue = mCoins.get(r)
            val currentDenomMin = getDenomMin(r, c - currentDenomValue) + 1
            val previousDenomMin = getDenomMin(r - 1, c)
            if (c == 0) {
                table[r][c] = 0
            } else table[r][c] = Math.min(currentDenomMin, previousDenomMin)
        }
    }
}

fun getDenomMin(r: Int, c: Int): Int {
    if (r < 0 || c < 0) return maxValue
    else return table[r][c]
}

fun printT(amt: Int) {
    for (r in 0..mCoins.size - 1) {
        for (c in 0..amt) {
            print("${table[r][c]} ")
        }
        println("")
    }
}