Add exponentiate_reverse.py — compute n ** reverse(n) (closes #1)

exponentiate_reverse.py

@@ -0,0 +1,63 @@
+#!/usr/bin/env python3
+"""exponentiate_reverse.py
+
+Compute n ** reverse(n). Example: 54 -> 54**45
+
+Usage:
+    python exponentiate_reverse.py 54
+
+Notes:
+- The reversed exponent is computed from the absolute value of the input's digits.
+- Very large results may be extremely big; use small inputs for quick runs.
+"""
+from __future__ import annotations
+import argparse
+import sys
+
+
+def reverse_int(n: int) -> int:
+    """Return the integer formed by reversing the decimal digits of n.
+
+    Examples:
+        54 -> 45
+        120 -> 21 (leading zeros dropped)
+        -13 -> 31
+    """
+    s = str(abs(n))
+    rs = s[::-1].lstrip("0") or "0"
+    rev = int(rs)
+    return rev if n >= 0 else rev
+
+
+def exponentiate_reverse(n: int) -> int:
+    """Return n ** reverse_int(n).
+
+    Uses the absolute reversed digits as the exponent (so the exponent is non-negative).
+    """
+    exp = reverse_int(n)
+    return pow(n, exp)
+
+
+def parse_args(argv: list[str] | None = None) -> argparse.Namespace:
+    p = argparse.ArgumentParser(
+        prog="exponentiate_reverse",
+        description="Compute n raised to the power formed by reversing the digits of n",
+    )
+    p.add_argument("n", type=int, help="integer base (e.g. 54)")
+    return p.parse_args(argv)
+
+
+def main(argv: list[str] | None = None) -> int:
+    args = parse_args(argv)
+    n = args.n
+    try:
+        result = exponentiate_reverse(n)
+    except OverflowError:
+        print("Result too large to compute with Python's pow()", file=sys.stderr)
+        return 2
+    print(result)
+    return 0
+
+
+if __name__ == "__main__":
+    raise SystemExit(main())