http://snippets.dzone.com/posts Fri, 29 Aug 2008 10:43:18 GMT DZone Snippets: permutation code http://snippets.dzone.com/posts/show/2353 // description of your code here <br /> <br /><code> <br />cdef class PermuteJ: <br /> <br /> cdef int n, first <br /> cdef int lst3[32] <br /> cdef object lst, lst2 <br /> <br /> def __init__(self, lst): <br /> cdef int i <br /> self.lst = lst <br /> self.lst2 = lst[:] <br /> self.first = 0 <br /> self.n = len(lst) - 1 <br /> if self.n >= 31: <br /> raise Exception, "Are you kidding?" <br /> for i from 0 <= i < len(lst): <br /> self.lst3[i] = i <br /> <br /> def __iter__(self): <br /> return self <br /> <br /> def __next__(self): <br /> cdef int j, l, k, x, y, z, sn, length, neg1, neg2, neg3 <br /> cdef int* sl <br /> cdef object output <br /> <br /> if self.first == 0: <br /> self.first = 1 <br /> return self.lst2 <br /> if self.n == 1: <br /> return [self.lst[1], self.lst[0]] <br /> <br /> sn = self.n <br /> length = sn + 1 <br /> sl = self.lst3 <br /> neg1 = sn <br /> neg2 = length - 2 <br /> neg3 = length - 3 <br /> while 1: <br /> if sl[neg2] < sl[neg1]: <br /> sl[neg2], sl[neg1] = sl[neg1], sl[neg2] <br /> elif sl[neg3] < sl[neg2]: <br /> if sl[neg3] < sl[neg1]: <br /> sl[neg3], sl[neg2], sl[neg1] = sl[neg1], sl[neg3], sl[neg2] <br /> else: <br /> sl[neg3], sl[neg2], sl[neg1] = sl[neg2], sl[neg1], sl[neg3] <br /> else: <br /> j = sn - 3 <br /> if j < 0: raise StopIteration <br /> y = sl[j] <br /> x = sl[neg3] <br /> z = sl[neg1] <br /> while y >= x: <br /> j = j - 1 <br /> if j < 0: raise StopIteration <br /> x = y <br /> y = sl[j] <br /> if y < z: <br /> sl[j] = z <br /> sl[j+1] = y <br /> sl[sn] = x <br /> else: <br /> l = neg2 <br /> while y >= sl[l]: <br /> l = l - 1 <br /> sl[j], sl[l] = sl[l], y <br /> sl[sn], sl[j+1] = sl[j+1], sl[sn] <br /> k = j + 2 <br /> l = neg2 <br /> while k < l: <br /> sl[k], sl[l] = sl[l], sl[k] <br /> k = k + 1 <br /> l = l - 1 <br /> <br /> lst = self.lst <br /> lst2 = self.lst2 <br /> for j from 0 <= j < length: <br /> lst2[j] = sl[j] <br /> <br /> return lst2 <br /> <br /></code> Wed, 02 Aug 2006 23:59:41 GMT http://snippets.dzone.com/posts/show/2353 llimllib (Bill Mill)