Added solution

Author: avidLearnerInProgress

reorder_linkedList_alternate_deque.cpp

@@ -0,0 +1,36 @@
+/**
+ * Definition for singly-linked list.
+ * struct ListNode {
+ *     int val;
+ *     ListNode *next;
+ *     ListNode(int x) : val(x), next(NULL) {}
+ * };
+ */
+class Solution {
+public:
+    void reorderList(ListNode* head) {
+        deque<ListNode*> d;
+        if(head == NULL) return;
+        ListNode *temp = head;
+        while(temp != NULL){
+            d.push_back(temp);
+            temp = temp->next;
+        }
+        d.pop_front(); //since temp = head and we dont need to consider the head again..
+        
+        while(d.size() > 0){
+            
+            head->next = d.back();
+            d.pop_back();
+            head = head->next;
+            
+            if(d.size() > 0){
+                head->next = d.front();
+                d.pop_front();
+                head = head->next;
+            }   
+        }
+        head->next = NULL;
+        
+    }
+};