### Summary

Add `sort/sleep_sort.py`: a novelty sleep-sort implementation with a simulated mode (safe for CI) and an optional real threaded mode.

### Files added
- sort/sleep_sort.py

### Notes
- File name is snake_case.
- Includes doctests; tested with `python -m doctest -v sort/sleep_sort.py`.
- Follows repository style.

If this addresses an issue, add: `Fixes #<issue-number>`

Author: NghiemNgocDuc

sorts/sleep_sort.py

@@ -0,0 +1,100 @@
+# Sleep sort (novelty) implementation
+# This provides a fast simulated mode (default) plus an optional real threaded mode.
+
+from typing import List
+import threading
+import time
+
+
+def sleep_sort(a: List[int], simulate: bool = True, scale: float = 0.01) -> None:
+    """
+    Sort the list a in-place using the sleep sort idea.
+
+    Behavior:
+    - Destructive: modifies list a.
+    - Only accepts integers (positive, zero, or negative).
+    - Default simulate=True runs instantly by simulating timed wake-ups (safe for tests/CI).
+    - If simulate=False the function spawns one thread per element and uses time.sleep;
+      use that mode only for small inputs (and beware of real waiting).
+    - scale (seconds per unit) applies only when simulate=False.
+
+    >>> a = [3, 1, 2]
+    >>> b = sorted(a)
+    >>> sleep_sort(a)  # simulated, fast
+    >>> a == b
+    True
+
+    >>> a = [0, 0, 1]
+    >>> sleep_sort(a)
+    >>> a
+    [0, 0, 1]
+
+    >>> a = [-2, 1, 0]
+    >>> sleep_sort(a)
+    >>> a == sorted([-2, 1, 0])
+    True
+
+    >>> sleep_sort([1.5, 2])  # non-integers not allowed
+    Traceback (most recent call last)
+    ...
+    TypeError: integers only please
+    """
+    # quick no-op for empty
+    if not a:
+        return
+
+    # type checks
+    if any(not isinstance(x, int) for x in a):
+        raise TypeError("integers only please")
+
+    # handle negatives by offsetting so all "sleep times" are non-negative
+    min_val = min(a)
+    offset = -min_val if min_val < 0 else 0
+
+    if simulate:
+        # Simulated wake-up: bucket by wake time (value + offset), preserve original order
+        buckets = {}
+        for idx, val in enumerate(a):
+            wake = val + offset
+            buckets.setdefault(wake, []).append((idx, val))
+        result: List[int] = []
+        for wake in sorted(buckets.keys()):
+            # append in original order to make stable when values equal
+            for _, val in buckets[wake]:
+                result.append(val)
+        a[:] = result
+        return
+
+    # Real threaded mode (be careful: this actually sleeps)
+    results: List[int] = []
+    lock = threading.Lock()
+
+    def worker(value: int) -> None:
+        # sleep proportional to value (after offset), then append to results
+        time.sleep((value + offset) * scale)
+        with lock:
+            results.append(value)
+
+    threads: List[threading.Thread] = []
+    for val in a:
+        t = threading.Thread(target=worker, args=(val,))
+        t.daemon = True
+        t.start()
+        threads.append(t)
+
+    # wait for threads to finish
+    for t in threads:
+        t.join()
+
+    # results is in the order threads woke up
+    a[:] = results
+
+
+def main() -> None:
+    a = [8, 3, 2, 7, 4, 6, 8]
+    sleep_sort(a)  # simulated (fast)
+    print("Sorted order is:", " ".join(map(str, a)))
+
+
+if __name__ == "__main__":
+    main()