Mega Code Archive
Set permutation for Array
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class Array
def powerset
num = 2**size
ps = Array.new(num, [])
self.each_index do |i|
a = 2**i
b = 2**(i+1) - 1
j = 0
while j < num-1
for j in j+a..j+b
ps[j] += [self[i]]
end
j += 1
end
end
ps
end
end
x = [1, 2, 3]
y = x.powerset
# y is now:
# [[], [1], [2], [1,2], [3], [1,3], [2,3], [1,2,3]]
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