Radix Sort (MSD)

function radixMSDSort(arr, lo = 0, hi = arr.length-1, d) {
  if (d === undefined) d = Math.max(...arr).toString().length - 1;
  if (lo >= hi || d < 0) return;
  const exp = Math.pow(10, d);
  const bk = Array.from({length: 10}, () => []);
  for (let i = lo; i <= hi; i++)
    bk[Math.floor(arr[i] / exp) % 10].push(arr[i]);
  let idx = lo;
  for (let b = 0; b < 10; b++) {
    const start = idx;
    for (const v of bk[b]) arr[idx++] = v;
    if (bk[b].length > 1)
      radixMSDSort(arr, start, idx-1, d-1);
  }
}

def radix_msd_sort(arr, lo=0, hi=None, d=None):
    if hi is None: hi = len(arr)-1
    if d is None: d = len(str(max(arr)))-1
    if lo >= hi or d < 0: return
    exp = 10 ** d
    bk = [[] for _ in range(10)]
    for i in range(lo, hi+1):
        bk[(arr[i]//exp) % 10].append(arr[i])
    idx = lo
    for b in range(10):
        start = idx
        for v in bk[b]: arr[idx] = v; idx += 1
        if len(bk[b]) > 1:
            radix_msd_sort(arr, start, idx-1, d-1)

void radixMSDSort(vector<int>& arr, int lo, int hi, int d) {
  if (lo >= hi || d < 0) return;
  int exp = (int)pow(10, d);
  vector<vector<int>> bk(10);
  for (int i = lo; i <= hi; i++)
    bk[(arr[i]/exp)%10].push_back(arr[i]);
  int idx = lo;
  for (int b = 0; b < 10; b++) {
    int start = idx;
    for (int v : bk[b]) arr[idx++] = v;
    if (bk[b].size() > 1)
      radixMSDSort(arr, start, idx-1, d-1);
  }
}

void RadixMSDSort(int[] arr, int lo, int hi, int d) {
  if (lo >= hi || d < 0) return;
  int exp = (int)Math.Pow(10, d);
  var bk = Enumerable.Range(0,10)
    .Select(_ => new List<int>()).ToArray();
  for (int i = lo; i <= hi; i++)
    bk[(arr[i]/exp) % 10].Add(arr[i]);
  int idx = lo;
  for (int b = 0; b < 10; b++) {
    int start = idx;
    foreach (int v in bk[b]) arr[idx++] = v;
    if (bk[b].Count > 1)
      RadixMSDSort(arr, start, idx-1, d-1);
  }
}

void radixMSDSort(int arr[], int lo, int hi, int d) {
  if (lo >= hi || d < 0) return;
  int exp = 1;
  for (int i = 0; i < d; i++) exp *= 10;
  // Distribute into 10 buckets by digit d
  // Recurse on each bucket with d-1
}