今天小编给大家分享一下怎么用Python递归式实现二叉树前序,中序,后序遍历的相关知识点，内容详细，逻辑清晰，相信大部分人都还太了解这方面的知识，所以分享这篇文章给大家参考一下，希望大家阅读完这篇文章后有所收获，下面我们一起来了解一下吧。
记忆点：
前序：VLR
中序：LVR
后序：LRV
举例：
一颗二叉树如下图所示：
则它的前序、中序、后序遍历流程如下图所示：
class Solution: def preorderTraversal(self, root: TreeNode): def preorder(root: TreeNode): if not root: return res.append(root.val) preorder(root.left) preorder(root.right) res = [] preorder(root) return res
class Solution: def inorderTraversal(self, root: TreeNode): def inorder(root: TreeNode): if not root: return inorder(root.left) res.append(root.val) inorder(root.right) res = [] inorder(root) return res
class Solution: def postorderTraversal(self, root: TreeNode): def postorder(root: TreeNode): if not root: return postorder(root.left) res.append(root.val) postorder(root.right) res = [] postorder(root) return res
class TreeNode: def __init__(self, val=0, left=None, right=None): self.val = val self.left = left self.right = right # 用列表递归创建二叉树 def createTree(root,list_n,i): if i <len(list_n): if list_n[i] == 'null': return None else: root = TreeNode(val = list_n[i]) root.left = createTree(root.left,list_n,2*i+1) root.right = createTree(root.right,list_n,2*i+2) return root return root class Solution: def preorderTraversal(self, root: TreeNode): # 前序 def preorder(root: TreeNode): if not root: return res.append(root.val) preorder(root.left) preorder(root.right) res = [] preorder(root) return res def inorderTraversal(self, root: TreeNode): # 中序 def inorder(root: TreeNode): if not root: return inorder(root.left) res.append(root.val) inorder(root.right) res = [] inorder(root) return res def postorderTraversal(self, root: TreeNode): # 后序 def postorder(root: TreeNode): if not root: return postorder(root.left) postorder(root.right) res.append(root.val) res = [] postorder(root) return res if __name__ == "__main__": root = TreeNode() list_n = [1,2,3,4,5,6,7,8,'null',9,10] root = createTree(root,list_n,0) s = Solution() res_pre = s.preorderTraversal(root) res_in = s.inorderTraversal(root) res_post = s.postorderTraversal(root) print(res_pre) print(res_in) print(res_post)
""" # Definition for a Node. class Node: def __init__(self, val=None, children=None): self.val = val self.children = children """ class Solution: def postorder(self, root: 'Node') -> List[int]: def seq(root): if not root: return res.append(root.val) for child in root.children: seq(child) res = [] seq(root) return res N叉树后序遍历 """ # Definition for a Node. class Node: def __init__(self, val=None, children=None): self.val = val self.children = children """ class Solution: def postorder(self, root: 'Node') -> List[int]: def seq(root): if not root: return for child in root.children: seq(child) res.append(root.val) res = [] seq(root) return res
以上就是“怎么用Python递归式实现二叉树前序,中序,后序遍历”这篇文章的所有内容，感谢各位的阅读！相信大家阅读完这篇文章都有很大的收获，小编每天都会为大家更新不同的知识，如果还想学习更多的知识，请关注亿速云行业资讯频道。
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