该网页看起来很有希望。
def next_permutation(seq, pred=cmp): """Like C++ std::next_permutation() but implemented as generator. Yields copies of seq.""" def reverse(seq, start, end): # seq = seq[:start] + reversed(seq[start:end]) + # seq[end:] end -= 1 if end <= start: return while True: seq[start], seq[end] = seq[end], seq[start] if start == end or start+1 == end: return start += 1 end -= 1 if not seq: raise StopIteration try: seq[0] except TypeError: raise TypeError("seq must allow random access.") first = 0 last = len(seq) seq = seq[:] # Yield input sequence as the STL version is often # used inside do {} while. yield seq[:] if last == 1: raise StopIteration while True: next = last - 1 while True: # Step 1. next1 = next next -= 1 if pred(seq[next], seq[next1]) < 0: # Step 2. mid = last - 1 while not (pred(seq[next], seq[mid]) < 0): mid -= 1 seq[next], seq[mid] = seq[mid], seq[next] # Step 3. reverse(seq, next1, last) # Change to yield references to get rid of # (at worst) |seq|! copy operations. yield seq[:] break if next == first: raise StopIteration raise StopIteration>>> for p in next_permutation([int(c) for c in "111222"]):... print p... [1, 1, 1, 2, 2, 2][1, 1, 2, 1, 2, 2][1, 1, 2, 2, 1, 2][1, 1, 2, 2, 2, 1][1, 2, 1, 1, 2, 2][1, 2, 1, 2, 1, 2][1, 2, 1, 2, 2, 1][1, 2, 2, 1, 1, 2][1, 2, 2, 1, 2, 1][1, 2, 2, 2, 1, 1][2, 1, 1, 1, 2, 2][2, 1, 1, 2, 1, 2][2, 1, 1, 2, 2, 1][2, 1, 2, 1, 1, 2][2, 1, 2, 1, 2, 1][2, 1, 2, 2, 1, 1][2, 2, 1, 1, 1, 2][2, 2, 1, 1, 2, 1][2, 2, 1, 2, 1, 1][2, 2, 2, 1, 1, 1]>>>2017-08-12
七年后，这是一个更好的算法（为清楚起见，更好）：
from itertools import permutationsdef unique_perms(series): return {"".join(p) for p in permutations(series)}print(sorted(unique_perms('1122')))
