1.1 二叉树的初始化
|
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
|
#initial of BinaryTree
class BinaryTree:
def __init__(self,rootObj):
self.val = rootObj
self.left = None
self.right = None
def insertLeft(self,newNode):
if self.left == None:
self.left = BinaryTree(newNode)
else:
t = BinaryTree(newNode)
t.left = self.left
self.left = t
def insertRight(self,newNode):
if self.right == None:
self.right = BinaryTree(newNode)
else:
t = BinaryTree(newNode)
t.right = self.right
self.right = t
|
1.2 创建一个二叉树
|
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
|
#create a BinaryTree [18,7,11,3,4,5,6,#,#,#,#,1,3,2,4]
# 18
# 7 11
#3 4 5 6
# 1 3 2 4
root = BinaryTree(18)
root.left = BinaryTree(7)
root.right = BinaryTree(11)
root.left.left = BinaryTree(3)
root.left.right = BinaryTree(4)
root.right.left = BinaryTree(5)
root.right.right = BinaryTree(6)
root.right.left.left = BinaryTree(1)
root.right.left.right = BinaryTree(3)
root.right.right.left = BinaryTree(2)
root.right.right.right = BinaryTree(4)
|
1.3 前序遍历
|
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
|
#递归版本
def PreOrder(self, node):
if node:
print(node.val)
self.PreOrder(node.left)
self.PreOrder(node.right)
#循环版本
def PreOrderLoop(self, node):
if node == None:
return
stack =[]
print(node.val)
stack.append(node)
node = node.left
while stack!=[] or node:
while node:
print(node.val)
stack.append(node)
node = node.left
node = stack[-1].right
stack.pop()
#ouput: 18 7 3 4 11 5 1 3 6 2 4
|
1.4 中序遍历
|
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
|
#递归版本
def InOrder(self, node):
if node:
self.InOrder(node.left)
print(node.val)
self.InOrder(node.right)
#循环版本
def InOrderLoop(self, node):
if node == None:
return None
stack = []
stack.append(node)
node = node.left
while stack!=[] or node:
while node:
stack.append(node)
node = node.left
print(stack[-1].val)
node = stack[-1].right
stack.pop()
#output：3 7 4 18 1 5 3 11 2 6 4
|
1.5 后序遍历
|
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
|
#递归
def PostOrder(self, node):
if node:
self.PostOrder(node.left)
self.PostOrder(node.right)
print(node.val)
#非递归
def PostOrderLoop(self, node):
if node == None:
return
stack =[]
stack.append(node)
pre = None
while stack!=[]:
node = stack[-1]
if ((node.left==None and node.right==None) or
(pre and (pre == node.left or pre ==node.right))):
print(node.val)
pre = node
stack.pop()
else:
if node.right:
stack.append(node.right)
if node.left:
stack.append(node.left)
#output:3 4 7 1 3 5 2 4 6 11 18
|
1.6 层序遍历
|
1
2
3
4
5
6
7
8
9
10
11
12
13
14
|
def LevelOrder(self, node):
if node == None:
return
stack = []
stack.append(node)
while stack!=[]:
node = stack[0]
if node.left:
stack.append(node.left)
if node.right:
stack.append(node.right)
print(node.val)
stack.pop(0)
output: 18 7 11 3 4 5 6 1 3 2 4
|
1.7 计算节点数
|
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
|
#递归版本
def CountNode(self, root):
if root == None:
return 0
return self.CountNode(root.left) + self.CountNode(root.right) + 1
#非递归版本
def CountNodeNotRev(self, root):
if root == None:
return 0
stack = []
stack.append(root)
index = 0
while index<len(stack):
if stack[index].left:
stack.append(stack[index].left)
if stack[index].right:
stack.append(stack[index].right)
index += 1
print(len(stack))
output: 11
|
1.8 计算树的深度
|
1
2
3
4
5
6
|
def getTreeDepth(self, root):
if root == None:
return 0
left = self.getTreeDepth(root.left) + 1
right = self.getTreeDepth(root.right) + 1
return left if left>right else right
|
1.9 计算树的叶子树
|
1
2
3
4
5
6
|
def countLeaves(self, root):
if root == None:
return 0
if root.left==None and root.right==None:
return 1
return self.countLeaves(root.left)+self.countLeaves(root.right)
|
1.10 获取第K层节点数
|
1
2
3
4
|
def getKLevel(self, root, K):
if root == None: return 0
if K == 1: return 1
return self.getKLevel(root.left, K-1)+self.getKLevel(root.right, K-1)
|
1.11 判断两颗二叉树是否相同
|
1
2
3
4
|
def StrucCmp(self, root1, root2):
if root1 == None and root2 == None: return True
elif root1 ==None or root2 == None: return False
return self.StrucCmp(root1.left, root2.left) and self.StrucCmp(root1.right, root2.right)
|
1.12 二叉树的镜像
|
1
2
3
4
5
6
7
|
def Mirror(self, root):
if root == None: return
tmp = root.left
root.left = root.right
root.right = tmp
self.Mirror(root.left)
self.Mirror(root.right)
|
1.13 找最低公共祖先节点
|
1
2
3
4
5
6
7
8
|
def findLCA(self, root, node1, node2):
if root == None: return
if root == node1 or root == node2: return root
left = self.findLCA(root.left, node1, node2)
right = self.findLCA(root.right, node1, node2)
if left and right:
return root
return left if left else right
|
1.14 获取两个节点的距离
|
1
2
3
4
5
6
7
8
9
10
11
12
|
def getDist(self, root, node1, node2):
lca = self.findLCA(root, node1, node2) #找最低公共祖宗节点
level1 = self.FindLevel(lca, node1) #祖节点到两个节点的距离
level2 = self.FindLevel(lca, node2)
return level1+level2
def FindLevel(self, node, target):
if node == None: return -1
if node == target: return 0
level = self.FindLevel(node.left, target)
if level == -1: level = self.FindLevel(node.right, target)
if level != -1: return level + 1
return -1
|
1.15 找一个节点的所有祖宗节点
|
1
2
3
4
5
6
7
|
def findAllAncestor(self, root, target):
if root == None: return False
if root == target: return True
if self.findAllAncestor(root.left, target) or self.findAllAncestor(root.right, target):
print(root.val)
return True
return False
|
到此这篇关于python二叉树常用算法总结的文章就介绍到这了,更多相关python二叉树常用算法，内容请搜索服务器之家以前的文章或继续浏览下面的相关文章希望大家以后多多支持服务器之家！
原文链接：https://bbs.huaweicloud.com/blogs/254847