Create 0019_Remove_nth_node_from_end_of_list.py

vJechsmayr · web-flow · commit 88c7a0377409 · 2020-05-06T21:14:31.000+02:00
vJechsmayr#11 Close the issue- tested on leetCode
diff --git a/LeetCode/0019_Remove_nth_node_from_end_of_list.py b/LeetCode/0019_Remove_nth_node_from_end_of_list.py
@@ -0,0 +1,36 @@
+# Definition for singly-linked list.
+# class ListNode:
+#     def __init__(self, val=0, next=None):
+#         self.val = val
+#         self.next = next
+
+class Solution:
+    def removeNthFromEnd(self, head: ListNode, n: int) -> ListNode:
+        
+        # use dummy head will make the removal of head node easier
+        dummy_head = ListNode(-1)
+        dummy_head.next = head
+        
+        # cur keeps iteration till the end
+        # prev_of_removal traverses to the previous node of the one of being removed
+        cur, prev_of_removal = dummy_head, dummy_head
+        
+        
+        while cur.next != None:
+            
+            # n-step delay for prev_of_removal
+            if n <= 0:
+                prev_of_removal = prev_of_removal.next
+                
+            cur = cur.next
+            
+            n -=1
+        
+        
+        # Remove the N-th node from end of list
+        n_th_node = prev_of_removal.next
+        prev_of_removal.next = n_th_node.next
+        
+        del n_th_node
+        
+        return dummy_head.next
