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Add recursive solution to leetcode 24

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Original file line number	Diff line number	Diff line change
`@@ -43,3 +43,22 @@ def swapPairs(self, head: ListNode) -> ListNode:`
`43`	`43`	`######################`
`44`	`44`	`# RECURSIVE SOLUTION #`
`45`	`45`	`######################`
	`46`	`+class RecursiveSolution:`
	`47`	`+ def swapPairs(self, head: ListNode) -> ListNode:`
	`48`	`+ # Base case: Undefined node or one node`
	`49`	`+ if (head is None) or (head.next is None):`
	`50`	`+ return head`
	`51`	`+`
	`52`	`+ left_node = head`
	`53`	`+ right_node = head.next`
	`54`	`+`
	`55`	`+ # Figure out the value of left_node for the next recursive call`
	`56`	`+ next_left = None`
	`57`	`+ if (head.next):`
	`58`	`+ next_left = right_node.next`
	`59`	`+`
	`60`	`+ # Swap the positions of the right node and left node`
	`61`	`+ left_node.next = self.swapPairs(next_left)`
	`62`	`+ right_node.next = left_node`
	`63`	`+`
	`64`	`+ return right_node`

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