1 class Solution(object): 2 def __init__(self): 3 self.List = list() 4 5 def rdfs(self,S): 6 if S != '': 7 length = len(S) 8 depth = len(self.List) 9 tempval = '' 10 tempdepth = 0 11 for i in range(length): 12 s = S[i] 13 if s != '-': 14 tempval += s 15 if i == length - 1: 16 while depth != tempdepth: 17 self.List.pop(-1) 18 depth = len(self.List) 19 parent = self.List[-1] 20 21 val = int(tempval) 22 t = TreeNode(val) 23 if parent.left == None: 24 parent.left = t 25 elif parent.right == None: 26 parent.right = t 27 28 else: 29 if tempval != '': 30 while depth != tempdepth: 31 self.List.pop(-1) 32 depth = len(self.List) 33 parent = self.List[-1] 34 35 val = int(tempval) 36 t = TreeNode(val) 37 if parent.left == None: 38 parent.left = t 39 self.List.append(t) 40 self.rdfs(S[i:]) 41 elif parent.right == None: 42 parent.right = t 43 self.List.append(t) 44 self.rdfs(S[i:]) 45 break 46 else: 47 tempdepth += 1 48 else: 49 return None 50 51 def recoverFromPreorder(self, S: str) -> 'TreeNode': 52 tempval = '' 53 length = len(S) 54 for i in range(length): 55 s = S[i] 56 if s != '-':#数字 57 tempval += s 58 if i == length - 1: 59 val = int(tempval) 60 root = TreeNode(val) 61 62 else:#遇到横线，数字结束 63 val = int(tempval) 64 root = TreeNode(val) 65 self.List.append(root) 66 self.rdfs(S[i:]) 67 self.List.pop(-1) 68 return root 69 return root