add 3 leetcodes

Jack-Lee-Hiter · Jack-Lee-Hiter · commit d1f54688ef53 · 2016-08-26T11:33:25.000+08:00
diff --git a/.idea/workspace.xml b/.idea/workspace.xml
diff --git a/Target Offer/链表中环的入口结点.py b/Target Offer/链表中环的入口结点.py
@@ -16,12 +16,12 @@ def MeetingNode(self, pHead):
         if pSlow == None:
             return None
         pFast = pSlow.next
-        while pSlow != None and pFast != None:
+        while pFast:
             if pSlow == pFast:
                 return pSlow
             pSlow = pSlow.next
             pFast = pFast.next
-            if pFast != None:
+            if pFast:
                 pFast = pFast.next
 
     def EntryNodeOfLoop(self, pHead):
diff --git a/leetcode/101. Symmetric Tree.py b/leetcode/101. Symmetric Tree.py
@@ -0,0 +1,59 @@
+'''
+Given a binary tree, check whether it is a mirror of itself (ie, symmetric around its center).
+
+For example, this binary tree [1,2,2,3,4,4,3] is symmetric:
+
+    1
+   / \
+  2   2
+ / \ / \
+3  4 4  3
+But the following [1,2,2,null,3,null,3] is not:
+    1
+   / \
+  2   2
+   \   \
+   3    3
+'''
+
+class TreeNode(object):
+    def __init__(self, x):
+        self.val = x
+        self.left = None
+        self.right = None
+
+class Solution(object):
+    # recursive
+    def isSymmetric(self, root):
+        return self.selfIsSymmetrical(root, root)
+    def selfIsSymmetrical(self, pRoot1, pRoot2):
+        if pRoot1 and pRoot2:
+            return pRoot1.val == pRoot2.val and self.selfIsSymmetrical(pRoot1.left, pRoot2.right) and self.selfIsSymmetrical(pRoot1.right, pRoot2.left)
+        else:
+            return pRoot1 == pRoot2
+
+    #iterative(BFS)
+    def isSymmetric2(self, root):
+        if root:
+            now = [root]
+            while now:
+                vals = [i.val if i else None for i in now]
+                if list(reversed(vals)) != vals:
+                    return False
+                else:
+                    now = [j for i in now if i for j in (i.left, i.right)]
+        return True
+
+    # iterative(DFS)
+    def isSymmetric3(self, root):
+        if root:
+            stack = [(root.left, root.right)]
+            while len(stack) > 0:
+                p, q = stack.pop()
+                if p and q and p.val == q.val:
+                    stack.append((p.left, q.right))
+                    stack.append((p.right, q.left))
+                elif p != q:
+                    return False
+        return True
+
diff --git a/leetcode/82. Remove Duplicates from Sorted List II.py b/leetcode/82. Remove Duplicates from Sorted List II.py
@@ -0,0 +1,26 @@
+'''
+Given a sorted linked list, delete all nodes that have duplicate numbers, leaving only distinct numbers from the original list.
+
+For example,
+Given 1->2->3->3->4->4->5, return 1->2->5.
+Given 1->1->1->2->3, return 2->3.
+'''
+# -*- coding:utf-8 -*-
+class ListNode:
+    def __init__(self, x):
+        self.val = x
+        self.next = None
+class Solution:
+    def deleteDuplication(self, head):
+        dummy = pre = ListNode(0)
+        dummy.next = head
+        while head and head.next:
+            if head.val == head.next.val:
+                while head and head.next and head.val == head.next.val:
+                    head = head.next
+                head = head.next
+                pre.next = head
+            else:
+                pre = pre.next
+                head = head.next
+        return dummy.next
diff --git a/leetcode/83. Remove Duplicates from Sorted List.py b/leetcode/83. Remove Duplicates from Sorted List.py
@@ -14,10 +14,6 @@ def __init__(self, x):
 
 class Solution(object):
     def deleteDuplicates(self, head):
-        """
-        :type head: ListNode
-        :rtype: ListNode
-        """
         pNode = head
         while pNode:
             while pNode.next and pNode.next.val == pNode.val:
