Nic wrote:
> Hello,
> I've a problem in defining a good Python code useful to articulate the
> following algorithm.
> Can you help me please?
> Thanks a bunch,
> Nic
>
> 1. Insert a number "n".
> Example: 3
>
> 2. List all the numbers < or = to n.
> Example: 1,2,3.
>
> 3. Combine the listed numbers each other.
> Example:
> 12
> 13
> 23
>
> 4. For each combination associate two letters a and b.
> Example:
> 12a
> 12b
> 13a
> 13b
> 23a
> 23b
>
> 5. Combine the new combinations each other, provided that combinations
> including the same couple of numbers (e.g. 12a and 12b) cannot be combined.
> Example:
> 12a 13a 23a
> 12a 13b 23a
> 12a 13b 23b
> 12b 13a 23a
> 12b 13b 23a
> 12b 13b 23b
>
> PS
> 12a 13a 23a and13a 23a 12a are the same thing.
This might get you some of the way:
def nkRange(n,k):
m = n - k + 1
indexer = range(0, k)
vector = range(1, k+1)
last = range(m, n+1)
yield vector
while vector != last:
high_value = -1
high_index = -1
for i in indexer:
val = vector[i]
if val > high_value and val < m + i:
high_value = val
high_index = i
for j in range(k - high_index):
vector[j+high_index] = high_value + j + 1
yield vector
X = [ ''.join(map(str,x)) + y for x in nkRange(3,2) for y in ['a','b']
]
print X
def kSubsets( alist, k ):
n = len(alist)
for vector in nkRange(n, k):
ret = []
for i in vector:
ret.append( alist[i-1] )
yield ret
Y = [ ''.join(x) + y for x in kSubsets( '123', 2 ) for y in ['a','b']]
print Y
['12a', '12b', '13a', '13b', '23a', '23b']
(a 'cross product' function may also help you - search this Group)
Gerard
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