seen [terminology]

Terminology¶

Usage¶

• Use for values, states, keys, or remainders encountered before.
• It commonly supports:
  • Duplicate detection
  • Cycle detection in generated states
  • Recurring-decimal detection
  • Value-to-position lookup
• It does not necessarily imply that a graph node has been fully processed.

seen = set()

while n != 1 and n not in seen:
    seen.add(n)
    total = 0
    while n > 0:
        n, digit = divmod(n, 10)
        total += digit * digit
    n = total

See 202. Happy Number.