Sana Pournaghshband - Sharks - Section A

linked_lists/intersection.py

@@ -11,4 +11,26 @@ def intersection_node(headA, headB):
     """ Will return the node at which the two lists intersect.
         If the two linked lists have no intersection at all, return None.
     """
-    pass
+
+    '''
+    The algorithm is: Hashset
+    1.Store all the elements of headA in a hashset
+    2.Iterate through the headB and check for the first match and then return it.
+    Time Complexity - O(n+m)
+    Space Complexity - O(n)
+    '''
+    first_set = set()
+    curr = headA
+
+    while curr:
+        first_set.add(curr)
+        curr = curr.next
+
+    curr = headB
+    while curr:
+        if curr in first_set:
+            return curr
+        curr = curr.next
+
+    return None
+