Create Day 16 Odd Even Linked List.cpp

Author: tusharjaiswal123

Day 16 Odd Even Linked List.cpp

@@ -0,0 +1,66 @@
+PROBLEM:
+
+
+Given a singly linked list, group all odd nodes together followed by the even nodes. Please note here we are talking about the
+node number and not the value in the nodes.
+
+You should try to do it in place. The program should run in O(1) space complexity and O(nodes) time complexity.
+
+Example 1:
+Input: 1->2->3->4->5->NULL
+Output: 1->3->5->2->4->NULL
+
+Example 2:
+Input: 2->1->3->5->6->4->7->NULL
+Output: 2->3->6->7->1->5->4->NULL
+
+Note:
+The relative order inside both the even and odd groups should remain as it was in the input.
+The first node is considered odd, the second node even and so on ...
+
+
+SOLUTION:
+
+
+/**
+ * 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* oddEvenList(ListNode* head) {
+        
+        if(head==NULL)
+            return NULL;
+        
+        ListNode *result=head,*p1,*p2,*even,*p3;
+        p1=head;
+        p2=head->next;
+        even=p2;
+        
+        while(p1!=NULL && p2!=NULL)
+        {
+            p3=p2->next;
+            if(p3==NULL)
+                break;
+            
+            p1->next=p1->next->next;
+            p2->next=p2->next->next;
+            
+            p1=p1->next;
+            p2=p2->next;
+        }
+        
+        p1->next=even;
+        
+        return result;
+        
+        
+    }
+};