[IMP] Trees-2

construct-binary-tree-from-inorder-and-postorder-traversal.py

@@ -0,0 +1,31 @@
+''' 
+Time Complexity : O(n)
+Space Complexity : O(h)
+Did this code successfully run on Leetcode : Yes
+Any problem you faced while coding this :  No
+'''
+
+class Solution:
+
+    def buildTree(self, inorder, postorder):
+            self.hashmap={}
+            self.idx = len(inorder)-1
+
+            for i in range(len(inorder)):
+                self.hashmap[inorder[i]] = i
+            print(self.hashmap)
+
+            return self.helper(postorder,0,len(inorder)-1)
+
+    def helper(self,postorder,start,end):
+        if start > end:
+            return None
+        rootval = postorder[self.idx]
+        print(rootval)
+        root_idx = self.hashmap[rootval]
+        self.idx -= 1
+
+        root = TreeNode(rootval)
+        root.right = self.helper(postorder,root_idx+1,end)
+        root.left = self.helper(postorder,start,root_idx-1)
+        return root

sum-root-to-leaf-numbers.py

@@ -0,0 +1,39 @@
+''' 
+Time Complexity : O(n) 
+Space Complexity : O(h) 
+Did this code successfully run on Leetcode : Yes
+Any problem you faced while coding this :  No
+'''
+
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+
+    def __init__(self):
+        self.total = 0
+
+    def helper(self, root, numCount):
+        if root == None:
+            return
+
+        numCount = numCount * 10 + root.val
+
+        if root.left == None and root.right == None:
+            self.total += numCount
+
+        self.helper(root.left, numCount)
+        self.helper(root.right, numCount)
+
+
+    def sumNumbers(self, root):
+        if root == None:
+            return
+
+        self.helper(root, 0)
+
+        return self.total
+