Create Swap-nodes-in-pairs.cpp (codedecks-in#200)

* Create Swap-nodes-in-pairs.cpp * Update Swap-nodes-in-pairs.cpp

Author: lokeshsinghi

C++/Swap-nodes-in-pairs.cpp

@@ -0,0 +1,24 @@
+/**
+ * Definition for singly-linked list.
+ * struct ListNode {
+ * int val;
+ * ListNode *next;
+ * ListNode() : val(0), next(nullptr) {}
+ * ListNode(int x) : val(x), next(nullptr) {}
+ * ListNode(int x, ListNode *next) : val(x), next(next) {}
+ * };
+ */
+class Solution {
+public:
+ ListNode* swapPairs(ListNode* head) {
+ if(head==NULL || head->next==NULL)
+ return head;
+ ListNode* p=head->next;
+ head->next=swapPairs(head->next->next);
+ p->next=head;
+ return p;
+ }
+};
+
+// Time Complexity: O(N)
+// Space Complexity: O(1)