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Kotlin set Array as key for a HashMap

I'm doing a bit of Leetcode, and I'm facing this issue: Group Anagrams, I have a Python background and I can do the following:
res = defaultdic(list)
count = [0] * 26
res[tuple(count)].append(s)
as we can see we can set the tupled array as the key for the dictionary, I want to do the same thing in Kotlin, however, when creating this in Kotlin, I get a different object every time when adding this logic in a for loop.
fun groupAnagrams(strs: Array<String>): List<List<String>> {
val hashMap = hashMapOf<IntArray, ArrayList<String>>()
for (word in strs) {
val array = IntArray(26) { 0 }
for (char in word) {
val charInt = char - 'a'
array[charInt] += 1
}
if (hashMap.containsKey(array)) {
hashMap[array]!!.add(word)
} else {
hashMap[array] = ArrayList<String>().apply { add(word) }
}
}
return hashMap.values.toList()
}
Is this something can be done in Kotlin?

Equality for IntArray is checked based on its reference. You can use a List here in place of IntArray. Two Lists are equal if they contain the same elements.
Modified code will be like this:
fun groupAnagrams(strs: Array<String>): List<List<String>> {
val hashMap = hashMapOf<List<Int>, ArrayList<String>>()
for (word in strs) {
val array = List(26) { 0 }.toMutableList()
for (char in word) {
val charInt = char - 'a'
array[charInt] += 1
}
if (hashMap.containsKey(array)) {
hashMap[array]!!.add(word)
} else {
hashMap[array] = ArrayList<String>().apply { add(word) }
}
}
return hashMap.values.toList()
}

Avoiding the problem you run into (equality of arrays) by using String keys:
fun groupAnagramsWithHashing(strs: Array<String>): List<List<String>> {
val map = hashMapOf<String, MutableList<String>>()
MessageDigest.getInstance("SHA-1").also { sha ->
for (word in strs) {
word.toByteArray().sorted().forEach { sha.update(it) }
val key = sha.digest().joinToString()
map.computeIfAbsent(key) { mutableListOf() }.add(word)
}
}
return map.values.toList()
}
fun main() {
val input = arrayOf("eat", "tea", "tan", "ate", "nat", "bat")
groupAnagramsWithHashing(input).also { println(it) }
// [[eat, tea, ate], [bat], [tan, nat]]
}

Use python to rewrite if-else statements like javascript object literals

Here is an example of if-else statement in javascript.
function getTranslation(rhyme) {
if (rhyme.toLowerCase() === "apples and pears") {
return "Stairs";
} else if (rhyme.toLowerCase() === "hampstead heath") {
return "Teeth";
} else if (rhyme.toLowerCase() === "loaf of bread") {
return "Head";
} else if (rhyme.toLowerCase() === "pork pies") {
return "Lies";
} else if (rhyme.toLowerCase() === "whistle and flute") {
return "Suit";
}
return "Rhyme not found";
}
A more elegant way is to rewrite the if-else implementation using object.
function getTranslationMap(rhyme) {
const rhymes = {
"apples and pears": "Stairs",
"hampstead heath": "Teeth",
"loaf of bread": "Head",
"pork pies": "Lies",
"whistle and flute": "Suit",
};
return rhymes[rhyme.toLowerCase()] ?? "Rhyme not found";
}
Can python be used to write similar elegant code like javascript object literals?
I am using python 3.8
Javascript code segment is from link below;
https://betterprogramming.pub/dont-use-if-else-and-switch-in-javascript-use-object-literals-c54578566ba0

Python equivalent:
def get_translation_map(rhyme):
rhymes = {
"apples and pears": "Stairs",
"hampstead heath": "Teeth",
"loaf of bread": "Head",
"pork pies": "Lies",
"whistle and flute": "Suit"
}
return rhymes.get(rhyme.lower(), "Rhyme not found")
Another useful variation if you don't know the content of the dict and want to ensure a value is always returned:
v = adict.get('whatever') or 'default'
Would get a default value even if a there was a key with a None value in the dict

Greatest Small date

I have a two date columns let's say A and B in two separate tables. A contains the information of the date of test and column B contains date at which the factory was calibrated. I want to extract information of how many days has been passed since the factory was last calibrated.
For example:
A=['2020-02-26', '2020-02-27', '2020-02-28', '2020-02-29']
B=['2020-02-24', '2020-02-28']
Days_Passed since last calibration corresponding to A are [2,3,0,1]

Take the smallest date as reference 0 and convert other dates into days with respect to 0(smallest date)
A = [2,3,4,5]
B = [0,4]
for each value of A, perform a binary search to find the nearest smallest or equal value in B... Their subtraction will be the Days_Passed since the last calibration.
Answer Array = [2,3,0,1].

if dates in A and B be in order, this could be done in O(n+m) where n and m are the length of A and B. though you didn't mention about the programming language, this is the implementation in C#
the main part:
foreach (var testedDate in testedDates)
{
if (nextCalibratedDate.HasValue && (testedDate - nextCalibratedDate.Value).Days >= 0)
{
Console.WriteLine((testedDate - nextCalibratedDate.Value).Days);
calibratedDate = nextCalibratedDate.Value;
if (enumerator.MoveNext())
{
nextCalibratedDate = (DateTime?)enumerator.Current;
}
}
else
{
Console.WriteLine((testedDate - calibratedDate).Days);
}
}
and this is the complete code:
public static void Main(string[] args)
{
string[] A = new[] { "2020-02-26", "2020-02-27", "2020-02-28", "2020-02-29" };
string[] B = new[] { "2020-02-24", "2020-02-28" };
var testedDates = A
.Select(x => DateTime.Parse(x))
.ToArray();
var calibratedDates = B
.Select(x => DateTime.Parse(x))
.ToArray();
var enumerator = calibratedDates.GetEnumerator();
enumerator.MoveNext();
var calibratedDate = (DateTime)enumerator.Current;
DateTime? nextCalibratedDate = default;
if (enumerator.MoveNext())
{
nextCalibratedDate = (DateTime?)enumerator.Current;
}
foreach (var testedDate in testedDates)
{
if (nextCalibratedDate.HasValue && (testedDate - nextCalibratedDate.Value).Days >= 0)
{
Console.WriteLine((testedDate - nextCalibratedDate.Value).Days);
calibratedDate = nextCalibratedDate.Value;
if (enumerator.MoveNext())
{
nextCalibratedDate = (DateTime?)enumerator.Current;
}
}
else
{
Console.WriteLine((testedDate - calibratedDate).Days);
}
}
}

Swift range exceeds data length

I have a python server that I write and read from, using the stream delegate. It works fine but when I start a match and the server sends data back it crashes.
Here's where it crashes:
func checkForMessages() {
while true {
if inputBuffer.length < 4 {
print("buffer length\(inputBuffer.length)")
print( MemoryLayout.size(ofValue: Int()))
print("application quit here")
return
}
var msgLength = (inputBuffer.bytes).load(as: UInt32.self)
msgLength = UInt32(bigEndian: msgLength)
print(inputBuffer.length)
print(msgLength)
if inputBuffer.length < msgLength {
print("its returning here!")
return
}
// ******Crashes on the line Below******
let message: Data? = inputBuffer.subdata(with: NSRange(location: 4, length: Int(msgLength)))
processMessage(message!)
let amtRemaining: Int = inputBuffer.length - Int(msgLength) - 4
if amtRemaining == 0 {
inputBuffer = NSMutableData()
}
else {
print("Creating input buffer of length \(amtRemaining)")
inputBuffer = NSMutableData(bytes: inputBuffer.bytes + 4 + Int(msgLength), length: amtRemaining)
}
}
}
It crashes when setting "let message".
I have tried a couple of things like trying to mess with the range itself but I'm just not quite sure why its doing what its doing, I can post the server code used to send the message back if needed.

So the problem was fixed by replacing the following part of the code:
if inputBuffer.length < msgLength {
return
}
with
if inputBuffer.length < msgLength + 4 {
return
}

hex/binary string conversion in Swift

Python has two very useful library method (binascii.a2b_hex(keyStr) and binascii.hexlify(keyBytes)) which I have been struggling with in Swift. Is there anything readily available in Swift. If not, how would one implement it? Given all the bounds and other checks (like even-length key) are done.

Data from Swift 3 has no "built-in" method to print its contents as
a hex string, or to create a Data value from a hex string.
"Data to hex string" methods can be found e.g. at How to convert Data to hex string in swift or How can I print the content of a variable of type Data using Swift? or converting String to Data in swift 3.0. Here is an implementation from the first link:
extension Data {
func hexEncodedString() -> String {
return map { String(format: "%02hhx", $0) }.joined()
}
}
Here is a possible implementation of the reverse "hex string to Data"
conversion (taken from Hex String to Bytes (NSData) on Code Review, translated to Swift 3 and improved)
as a failable inititializer:
extension Data {
init?(fromHexEncodedString string: String) {
// Convert 0 ... 9, a ... f, A ...F to their decimal value,
// return nil for all other input characters
func decodeNibble(u: UInt8) -> UInt8? {
switch(u) {
case 0x30 ... 0x39:
return u - 0x30
case 0x41 ... 0x46:
return u - 0x41 + 10
case 0x61 ... 0x66:
return u - 0x61 + 10
default:
return nil
}
}
self.init(capacity: string.utf8.count/2)
var iter = string.utf8.makeIterator()
while let c1 = iter.next() {
guard
let val1 = decodeNibble(u: c1),
let c2 = iter.next(),
let val2 = decodeNibble(u: c2)
else { return nil }
self.append(val1 << 4 + val2)
}
}
}
Example:
// Hex string to Data:
if let data = Data(fromHexEncodedString: "0002468A13579BFF") {
let idata = Data(data.map { 255 - $0 })
// Data to hex string:
print(idata.hexEncodedString()) // fffdb975eca86400
} else {
print("invalid hex string")
}

Not really familiar with Python and the checks it performs when convert the numbers, but you can expand the function below:
func convert(_ str: String, fromRadix r1: Int, toRadix r2: Int) -> String? {
if let num = Int(str, radix: r1) {
return String(num, radix: r2)
} else {
return nil
}
}
convert("11111111", fromRadix: 2, toRadix: 16)
convert("ff", fromRadix: 16, toRadix: 2)

Swift 2
extension NSData {
class func dataFromHexString(hex: String) -> NSData? {
let regex = try! NSRegularExpression(pattern: "^[0-9a-zA-Z]*$", options: .CaseInsensitive)
let validate = regex.firstMatchInString(hex, options: NSMatchingOptions.init(rawValue: 0), range: NSRange(location: 0, length: hex.characters.count))
if validate == nil || hex.characters.count % 2 != 0 {
return nil
}
let data = NSMutableData()
for i in 0..<hex.characters.count/2 {
let hexStr = hex.substring(i * 2, length: 2)
var ch: UInt32 = 0
NSScanner(string: hexStr).scanHexInt(&ch)
data.appendBytes(&ch, length: 1)
}
return data
}
}
let a = 0xabcd1234
print(String(format: "%x", a)) // Hex to String
NSData.dataFromHexString("abcd1234") // String to hex