From 714a4cb00651fd22fd2f5e8a4f2fff816f5b0d83 Mon Sep 17 00:00:00 2001
From: Meng Wei <weimeng@weimengs-MacBook-Air.local>
Date: Thu, 11 Jan 2018 00:04:02 -0800
Subject: [PATCH] Reversed 2 linked list. Today we shared the song OldStreet.
 Time is really slow on the old street.

---
 206-reverse-linked-list-in-two-ways | 34 ++++++++++++++++++++++
 92-reverse-linked-list-II           | 44 +++++++++++++++++++++++++++++
 2 files changed, 78 insertions(+)
 create mode 100644 206-reverse-linked-list-in-two-ways
 create mode 100644 92-reverse-linked-list-II

diff --git a/206-reverse-linked-list-in-two-ways b/206-reverse-linked-list-in-two-ways
new file mode 100644
index 0000000..b9010fe
--- /dev/null
+++ b/206-reverse-linked-list-in-two-ways
@@ -0,0 +1,34 @@
+# Definition for singly-linked list.
+# class ListNode(object):
+#     def __init__(self, x):
+#         self.val = x
+#         self.next = None
+
+# EASY
+# Iteratively: T:O(N) S:O(1)
+# Recursively: T:O(N) S:O(N)
+class Solution(object):
+    def reverseList(self, head):
+        """
+        :type head: ListNode
+        :rtype: ListNode
+        """
+        # Iteratively 
+        # rev = None
+        # while head!=None:
+        #     temp = head.next
+        #     head.next = rev
+        #     rev = head
+        #     head = temp
+        # return rev
+        
+        # Recursively
+        return self._reverse(head,None)
+    
+    def _reverse(self,head,prev):
+        if head == None:
+            return prev
+        else:
+            temp = head.next
+            head.next = prev
+            return self._reverse(temp,head)
diff --git a/92-reverse-linked-list-II b/92-reverse-linked-list-II
new file mode 100644
index 0000000..b67eaaa
--- /dev/null
+++ b/92-reverse-linked-list-II
@@ -0,0 +1,44 @@
+# Medium
+# O(N) O(1)
+
+
+# Definition for singly-linked list.
+# class ListNode(object):
+#     def __init__(self, x):
+#         self.val = x
+#         self.next = None
+
+class Solution(object):
+    def reverseBetween(self, head, m, n):
+        """
+        :type head: ListNode
+        :type m: int
+        :type n: int 
+        :rtype: ListNode
+        """
+        i = 0
+        if(m==n):
+            return head
+        dummy = ListNode(0)
+        dummy.next = head
+        ret = dummy
+        while dummy:
+            if i+1==m:
+                dummy.next = self.reverseBegin(dummy.next, n-i)
+                return ret.next
+            i += 1
+            dummy = dummy.next
+            
+    def reverseBegin(self, node, k):
+        i = 0
+        rev = None
+        ret = node
+        while i<k:
+            i += 1
+            temp = node.next
+            node.next= rev
+            rev = node
+            node = temp
+        ret.next = temp
+        return rev
+