leetcode new problems

leetcode/lc24/SwapNodes.cpp

@@ -0,0 +1,30 @@
+class Solution{
+    public: 
+        ListNode* SwapNode(ListNode* head){
+            if(!head || !head->next) return head;
+
+            ListNode* dummy = new ListNode(0);
+            dummy->next = head;
+
+            ListNode* cur = head;
+            ListNode* prev = dummy;
+
+            while(cur && cur->next){
+                ListNode* nextPair = cur->next->next;
+                ListNode* second = cur->next;
+
+                second->next = cur;
+                cur->next = nextPair;
+                prev->next = second;
+
+                prev = cur;
+                cur = nextPair;
+            }
+            ListNode* newHead = dummy->next;
+            delete dummy;
+            return newHead;
+        }
+};
+
+//TC : O(n)
+//SC : O(1)