Leetcode 19

Python solution

Author: kyle8998

README.md

@@ -20,6 +20,7 @@ Personal Practice Set - Doing One a Day (sometimes) in a Variety of Languages!!
 | 14 | Easy       | [Longest Common Prefix](leetcode/14-Easy-Longest-Common-Prefix/problem.md)                   | [Python](leetcode/14-Easy-Longest-Common-Prefix/answer.py)       |
 | 15 | Medium     | [3Sum](leetcode/15-Medium-3Sum/problem.md)                                                   | [Python](leetcode/15-Medium-3Sum/answer.py)                      |
 | 16 | Medium     | [3Sum Closest](leetcode/16-Medium-3Sum-Closest/problem.md)                                   | [Python](leetcode/16-Medium-3Sum-Closest/answer.py)              |
+| 19 | Medium     | [Remove Nth Node From End of List](leetcode/19-Medium-Remove-Nth-Node-From-End-Of-List/problem.md) | [Python](leetcode/19-Medium-Remove-Nth-Node-From-End-Of-List/answer.py) |
 | 20 | Easy       | [Valid Parentheses](leetcode/20-Easy-Valid-Parentheses/problem.md)                           | [Java](leetcode/20-Easy-Valid-Parentheses/answer.java)           |
 | 21 | Easy       | [Merge Two Sorted Lists](leetcode/21-Easy-Merge-Two-Sorted-Lists/problem.md)                 | [Java](leetcode/21-Easy-Merge-Two-Sorted-Lists/answer.java)      |
 | 22 | Medium     | [Generate Parentheses](leetcode/22-Medium-Generate-Parentheses/problem.md)                   | [Python](leetcode/22-Medium-Generate-Parentheses/answer.py)      |

leetcode/19-Medium-Remove-Nth-Node-From-End-Of-List/answer.py

@@ -0,0 +1,43 @@
+#!/usr/bin/python
+
+#------------------------------------------------------------------------------
+
+# Definition for singly-linked list.
+# class ListNode:
+#     def __init__(self, x):
+#         self.val = x
+#         self.next = None
+
+class Solution:
+    def removeNthFromEnd(self, head, n):
+        """
+        :type head: ListNode
+        :type n: int
+        :rtype: ListNode
+        """
+        if head:
+            fast = head
+            slow = head
+        
+            for _ in range(n):
+                if fast:
+                    fast = fast.next
+                else:
+                    return None
+                
+            # head case
+            if not fast:
+                head = head.next
+                return head
+                
+            # This will bring slow up to the correct node
+            while fast.next:
+                fast = fast.next
+                slow = slow.next
+                
+            # Remove the node after slow
+            slow.next = slow.next.next
+            return head
+                
+#------------------------------------------------------------------------------
+#Testing

leetcode/19-Medium-Remove-Nth-Node-From-End-Of-List/problem.md

@@ -0,0 +1,24 @@
+# Problem 19: Remove Nth Node From End of List
+
+
+#### Difficulty: Medium
+
+#### Problem
+
+Given a linked list, remove the nth node from the end of list and return its head.
+
+**Note:**
+
+Given n will always be valid.
+Try to do this in one pass.
+
+
+#### Example
+
+<pre>
+
+   Given linked list: 1->2->3->4->5, and n = 2.
+
+   After removing the second node from the end, the linked list becomes 1->2->3->5.
+
+</pre>