human
Combinations where every element appears twice and distance between appearances is equal to the value | Find all combinations that satisfies given constraints.
if all elements are filled , print the solution.
Try all possible combinations for element elem.
if position i and ( i + elem + 1 ) are not occupied in the vector.
place elem at position i and ( i + elem + 1 ).
recurse for next element.
backtrack ( remove elem from position i and ( i + elem + 1 ) ).
create a vector of double the size of given number with.
all its elements initialized by 1.
start from element 1.
given number"
How can the above be solved in Python?
 Can you provide a code to combinations where every element appears twice and distance between appearances is equal to the value and the other steps required?
assistant
#Here is code to combinations where every element appears twice and distance between appearances is equal to the value and the other steps required.
 def allCombinationsRec ( arr , elem , n ) :
	if ( elem > n ) :
		for i in ( arr ) :
			print ( i , end = " ▁ " )
		print ( " " )
		return
	for i in range ( 0 , 2 * n ) :
		if ( arr [ i ] == - 1 and ( i + elem + 1 ) < 2 * n and arr [ i + elem + 1 ] == - 1 ) :
			arr [ i ] = elem
			arr [ i + elem + 1 ] = elem
			allCombinationsRec ( arr , elem + 1 , n )
			arr [ i ] = - 1
			arr [ i + elem + 1 ] = - 1
def allCombinations ( n ) :
	arr = [ - 1 ] * ( 2 * n )
	elem = 1
	allCombinationsRec ( arr , elem , n )
n = 3
allCombinations ( n )