322. Coin Change

    func coinChange(_ coins: [Int], _ amount: Int) -> Int {
        var arr = [Int](repeating: Int.max, count:amount + 1)
        arr[0] = 0

        for i in stride(from: 1, through: amount, by : 1){
            for coin in coins{
                if i - coin >= 0 && arr[i - coin] != Int.max {
                    arr[i] = min(arr[i], arr[i - coin] + 1)
                }
            }
        }
        if arr[amount] == Int.max { return -1}
        return arr[amount]
    }