(prev, root, sum)
| 42 | return False |
| 43 | |
| 44 | def helper(prev, root, sum): |
| 45 | if prev + root.val == sum: |
| 46 | if not root.left and not root.right: |
| 47 | return True |
| 48 | |
| 49 | if root.left: |
| 50 | if helper(prev + root.val, root.left, sum): |
| 51 | return True |
| 52 | |
| 53 | if root.right: |
| 54 | if helper(prev + root.val, root.right, sum): |
| 55 | return True |
| 56 | |
| 57 | return False |
| 58 | |
| 59 | return helper(0, root, sum) |