[codex] Optimize sum root to leaf numbers

practice/leetcode/solutions_00000/solution_00129.py

@@ -18,71 +18,18 @@ def sumNumbers(self, root):
         :type root: TreeNode
         :rtype: int
         """
-        acc = []
-
-        def rec(root, path, pathLen):
+        def rec(root, total):
             if not root:
-                return
-
-            if len(path) > pathLen:
-                path[pathLen] = str(root.val)
-            else:
-                path.append(str(root.val))
+                return 0
 
-            pathLen += 1
+            total = total * 10 + root.val
 
             if root.left is None and root.right is None:
-                acc.append(int(''.join(path[:pathLen])))
-            else:
-                rec(root.left, path, pathLen)
-                rec(root.right, path, pathLen)
-
-        path = []
-        rec(root, path, 0)
-
-        return sum(acc)
-
+                return total
 
-class Solution2(object):
-    def sumNumbers(self, root):
-        """
-        :type root: TreeNode
-        :rtype: int
-        """
-        if not root:
-            return 0
+            return rec(root.left, total) + rec(root.right, total)
 
-        def root_to_leaf_pathes(d, child):
-            q = [child]
-            while True:
-                parent = d.get(q[0])
-                if not parent:
-                    break
-                q.insert(0, parent)
-
-            res = int(''.join([str(n.val) for n in q]))
-
-            return res
-
-        stack, parent = [root], {}
-        parent[root] = None
-        sum_ = 0
-
-        while stack:
-
-            node = stack.pop()
-
-            if node.left is None and node.right is None:
-                sum_ += root_to_leaf_pathes(parent, node)
-
-            if node.left:
-                parent[node.left] = node
-                stack.append(node.left)
-            if node.right:
-                parent[node.right] = node
-                stack.append(node.right)
-
-        return sum_
+        return rec(root, 0)
 
 
 class TestSolution(unittest.TestCase):
@@ -98,9 +45,6 @@ def test_sumNumbers(self):
 
         self.assertEqual(solution.sumNumbers(root), 1026)
 
-        solution2 = Solution2()
-        self.assertEqual(solution2.sumNumbers(root), 1026)
-
 
 if __name__ == '__main__':
     unittest.main()