Create Merge Two Sorted Lists.CPP

C++ BASIC COURSE/Merge Two Sorted Lists.CPP

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+class Solution {
+public:
+	ListNode* mergeTwoLists(ListNode* l1, ListNode* l2) 
+  {
+		// if list1 happen to be NULL
+		// we will simply return list2.
+		if(l1 == NULL)
+        {
+			return l2;
+		}
+
+		// if list2 happen to be NULL
+		// we will simply return list1.
+		if(l2 == NULL)
+        {
+			return l1;
+		} 
+
+		// if value pointend by l1 pointer is less than equal to value pointed by l2 pointer
+		// we wall call recursively l1 -> next and whole l2 list.
+		if(l1 -> val <= l2 -> val)
+        {
+			l1 -> next = mergeTwoLists(l1 -> next, l2);
+			return l1;
+		}
+		// we will call recursive l1 whole list and l2 -> next
+		else
+        {
+			l2 -> next = mergeTwoLists(l1, l2 -> next);
+			return l2;            
+		}
+	}
+};