human
Give me a code to queries to calculate sum by alternating signs of array elements in a given range and the other steps required given the following:
Queries to calculate sum by alternating signs of array elements in a given range | Function to build the segment tree.
If current node is a leaf node of the segment tree.
Update tree [ index ].
Update tree [ index ].
Divide the segment tree.
Update on L segment tree.
Update on R segment tree.
Find the sum from L subtree and R subtree.
Function to update elements at index pos by val in the segment tree.
If current node is a leaf node.
If current index is even.
Update tree [ index ].
Update tree [ index ].
Divide the segment tree elements into L and R subtree.
If element lies in L subtree.
Update tree [ index ].
Function to find the sum of array elements in the range [ L , R ].
If start and end not lies in the range [ L , R ].
If start and end comleately lies in the range [ L , R ].
Stores sum from left subtree.
Stores sum from right subtree.
Driver code"
How can the above be solved in Python?
assistant
#Here is code to queries to calculate sum by alternating signs of array elements in a given range and the other steps required.
 def build ( tree , arr , start , end , index ) :
	if ( start == end ) :
		if ( start % 2 == 0 ) :
			tree [ index ] = arr [ start ]
		else :
			tree [ index ] = - arr [ start ]
		return
	mid = start + ( end - start ) // 2
	build ( tree , arr , start , mid , 2 * index + 1 )
	build ( tree , arr , mid + 1 , end , 2 * index + 2 )
	tree [ index ] = tree [ 2 * index + 1 ] + tree [ 2 * index + 2 ]
def update ( tree , index , start , end , pos , val ) :
	if ( start == end ) :
		if ( start % 2 == 0 ) :
			tree [ index ] = val
		else :
			tree [ index ] = - val
		return
	mid = start + ( end - start ) // 2
	if ( mid >= pos ) :
		update ( tree , 2 * index + 1 , start , mid , pos , val )
	else :
		update ( tree , 2 * index + 2 , mid + 1 , end , pos , val )
	tree [ index ] = tree [ 2 * index + 1 ] + tree [ 2 * index + 2 ]
def FindSum ( tree , start , end , L , R , index ) :
	if ( L > end or R < start ) :
		return 0
	if ( L <= start and R >= end ) :
		return tree [ index ]
	mid = start + ( end - start ) // 2
	X = FindSum ( tree , start , mid , L , R , 2 * index + 1 )
	Y = FindSum ( tree , mid + 1 , end , L , R , 2 * index + 2 )
	return X + Y
if __name__ == ' _ _ main _ _ ' :
	arr = [ 1 , 2 , 3 , 4 ]
	N = len ( arr )
	tree = [ 0 for i in range ( 4 * N + 5 ) ]
	build ( tree , arr , 0 , N - 1 , 0 )
	Q = [ [ 2 , 0 , 3 ] , [ 1 , 1 , 5 ] , [ 2 , 1 , 2 ] ]
	cntQuey = 3
	for i in range ( cntQuey ) :
		if ( Q [ i ] [ 0 ] == 1 ) :
			update ( tree , 0 , 0 , N - 1 , Q [ i ] [ 1 ] , Q [ i ] [ 2 ] )
		else :
			if ( Q [ i ] [ 1 ] % 2 == 0 ) :
				print ( FindSum ( tree , 0 , N - 1 , Q [ i ] [ 1 ] , Q [ i ] [ 2 ] , 0 ) , end = " ▁ " )
			else :
				print ( - FindSum ( tree , 0 , N - 1 , Q [ i ] [ 1 ] , Q [ i ] [ 2 ] , 0 ) , end = " ▁ " )