por ejemplo: Entrada: k = 3, n = 9
Salida: [[1,2,6], [1,3,5], [2,3,4]]
Entrada: k = 2, n = 5
Salida: [[1,4] [2,3]]
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from itertools import combinations
def num(k,n):
nums=[1,2,3,4,5,6,7,8,9]
res=[]
for i in range(len(nums)):
res +=list(combinations(nums,i))
res=[x for x in res if len(x) == k]
a=[]
for j in res:
if sum(j) ==n :
a.append(list(j))
return a