update

Author: kamyu104

C++/can-place-flowers.cpp

@@ -10,7 +10,7 @@ class Solution {
                 flowerbed[i] = 1;
                 --n;
             }
-            if (n  <= 0) {
+            if (n <= 0) {
                 return true;
             }
         }

Python/construct-string-from-binary-tree.py

@@ -0,0 +1,58 @@
+# Time:  O(n)
+# Space: O(h)
+
+# You need to construct a string consists of parenthesis and integers from a binary tree with
+# the preorder traversing way.
+#
+# The null node needs to be represented by empty parenthesis pair "()".
+# And you need to omit all the empty parenthesis pairs that don't affect 
+# the one-to-one mapping relationship between the string and the original binary tree.
+#
+# Example 1:
+# Input: Binary tree: [1,2,3,4]
+#       1
+#      /   \
+#     2     3
+#   /    
+#   4     
+#
+# Output: "1(2(4))(3)"
+#
+# Explanation: Originallay it needs to be "1(2(4)())(3()())", 
+# but you need to omit all the unnecessary empty parenthesis pairs. 
+# And it will be "1(2(4))(3)".
+# Example 2:
+# Input: Binary tree: [1,2,3,null,4]
+#       1
+#      /   \
+#     2     3
+#      \  
+#       4 
+#
+# Output: "1(2()(4))(3)"
+#
+# Explanation: Almost the same as the first example, 
+# except we can't omit the first parenthesis pair to break the one-to-one mapping relationship
+# between the input and the output.
+
+
+# Definition for a binary tree node.
+# class TreeNode(object):
+#     def __init__(self, x):
+#         self.val = x
+#         self.left = None
+#         self.right = None
+
+class Solution(object):
+    def tree2str(self, t):
+        """
+        :type t: TreeNode
+        :rtype: str
+        """
+        if not t: return ""
+        s = str(t.val)
+        if t.left or t.right:
+            s += "(" + self.tree2str(t.left) + ")"
+        if t.right:
+            s += "(" + self.tree2str(t.right) + ")"
+        return s