parent
2a1bb23990
commit
9eac1275f6
@ -1,10 +1,173 @@
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'''
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"""
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File: binary_search_tree.py
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Created Time: 2022-11-25
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Author: Krahets (krahets@163.com)
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'''
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"""
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import sys, os.path as osp
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sys.path.append(osp.dirname(osp.dirname(osp.abspath(__file__))))
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from include import *
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class BinarySearchTree:
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"""
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二叉搜索树
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"""
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def __init__(self, nums) -> None:
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nums.sort()
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self.__root = self.buildTree(nums, 0, len(nums) - 1)
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def buildTree(self, nums, start_index, end_index):
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if start_index > end_index:
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return None
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mid = (start_index + end_index) // 2
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root = TreeNode(nums[mid])
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root.left = self.buildTree(
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nums=nums, start_index=start_index, end_index=mid - 1
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)
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root.right = self.buildTree(nums=nums, start_index=mid + 1, end_index=end_index)
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return root
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def get_root(self):
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return self.__root
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def search(self, num):
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"""
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查找结点
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"""
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cur = self.get_root()
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# 循环查找,越过叶结点后跳出
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while cur is not None:
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# 目标结点在 root 的右子树中
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if cur.val < num:
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cur = cur.right
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# 目标结点在 root 的左子树中
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elif cur.val > num:
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cur = cur.left
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# 找到目标结点,跳出循环
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else:
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break
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return cur
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def insert(self, num):
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"""
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插入结点
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"""
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root = self.get_root()
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# 若树为空,直接提前返回
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if root is None:
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return None
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cur = root
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pre = None
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# 循环查找,越过叶结点后跳出
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while cur is not None:
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# 找到重复结点,直接返回
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if cur.val == num:
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return None
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pre = cur
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if cur.val < num: # 插入位置在 root 的右子树中
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cur = cur.right
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else: # 插入位置在 root 的左子树中
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cur = cur.left
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# 插入结点 val
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node = TreeNode(num)
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if pre.val < num:
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pre.right = node
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else:
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pre.left = node
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return node
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def remove(self, num):
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"""
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删除结点
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"""
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root = self.get_root()
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# 若树为空,直接提前返回
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if root is None:
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return None
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cur = root
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pre = None
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# 循环查找,越过叶结点后跳出
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while cur is not None:
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# 找到待删除结点,跳出循环
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if cur.val == num:
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break
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pre = cur
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if cur.val < num: # 待删除结点在 root 的右子树中
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cur = cur.right
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else: # 待删除结点在 root 的左子树中
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cur = cur.left
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# 若无待删除结点,则直接返回
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if cur is None:
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return None
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# 子结点数量 = 0 or 1
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if cur.left is None or cur.right is None:
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# 当子结点数量 = 0 / 1 时, child = null / 该子结点
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child = cur.left or cur.right
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# 删除结点 cur
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if pre.left == cur:
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pre.left = child
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else:
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pre.right = child
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# 子结点数量 = 2
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else:
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# 获取中序遍历中 cur 的下一个结点
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nex = self.min(cur.right)
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tmp = nex.val
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# 递归删除结点 nex
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self.remove(nex.val)
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# 将 nex 的值复制给 cur
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cur.val = tmp
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return cur
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def min(self, root):
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"""
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获取最小结点
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"""
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if root is None:
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return root
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# 循环访问左子结点,直到叶结点时为最小结点,跳出
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while root.left is not None:
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root = root.left
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return root
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if __name__ == "__main__":
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# 初始化二叉搜索树
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nums = list(range(1, 16))
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bst = BinarySearchTree(nums=nums)
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print("\n初始化的二叉树为\n")
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print_tree(bst.get_root())
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# 查找结点
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node = bst.search(5)
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print("\n查找到的结点对象为: {},结点值 = {}".format(node, node.val))
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# 插入结点
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ndoe = bst.insert(16)
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print("\n插入结点 16 后,二叉树为\n")
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print_tree(bst.get_root())
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# 删除结点
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bst.remove(1)
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print("\n删除结点 1 后,二叉树为\n")
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print_tree(bst.get_root())
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bst.remove(2)
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print("\n删除结点 2 后,二叉树为\n")
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print_tree(bst.get_root())
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bst.remove(4)
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print("\n删除结点 4 后,二叉树为\n")
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print_tree(bst.get_root())
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'''
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"""
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File: binary_tree.py
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Created Time: 2022-11-25
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Author: Krahets (krahets@163.com)
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'''
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"""
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import sys, os.path as osp
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sys.path.append(osp.dirname(osp.dirname(osp.abspath(__file__))))
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from include import *
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""" Driver Code """
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if __name__ == "__main__":
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# 初始化二叉树
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# 初始化节点
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n1 = TreeNode(val=1)
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n2 = TreeNode(val=2)
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n3 = TreeNode(val=3)
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n4 = TreeNode(val=4)
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n5 = TreeNode(val=5)
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n1.left = n2
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n1.right = n3
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n2.left = n4
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n2.right = n5
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print_tree(n1)
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# 插入与删除结点
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P = TreeNode(0)
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# 在 n1 -> n2 中间插入节点 P
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n1.left = P
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P.left = n2
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print_tree(n1)
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# 删除结点
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n1.left = n2
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print_tree(n1)
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'''
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"""
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File: binary_tree_bfs.py
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Created Time: 2022-11-25
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Author: Krahets (krahets@163.com)
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'''
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"""
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import sys, os.path as osp
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sys.path.append(osp.dirname(osp.dirname(osp.abspath(__file__))))
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from include import *
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def hierOrder(root):
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# 初始化队列,加入根结点
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queue = collections.deque()
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queue.append(root)
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# 初始化一个列表,用于保存遍历序列
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result = []
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while queue:
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# 队列出队
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node = queue.popleft()
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# 保存节点值
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result.append(node.val)
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if node.left is not None:
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# 左子结点入队
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queue.append(node.left)
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if node.right is not None:
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# 右子结点入队
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queue.append(node.right)
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return result
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""" Driver Code """
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if __name__ == "__main__":
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# 初始化二叉树
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# 这里借助了一个从数组直接生成二叉树的函数
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root = list_to_tree(
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arr=[1, 2, 3, 4, 5, 6, 7, None, None, None, None, None, None, None, None]
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)
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print("\n初始化二叉树\n")
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print_tree(root)
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# 层序遍历
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result = hierOrder(root)
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print("\n层序遍历的结点打印序列 = ", result)
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assert result == [1, 2, 3, 4, 5, 6, 7]
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'''
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"""
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File: binary_tree_dfs.py
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Created Time: 2022-11-25
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Author: Krahets (krahets@163.com)
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'''
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"""
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import sys, os.path as osp
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sys.path.append(osp.dirname(osp.dirname(osp.abspath(__file__))))
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from include import *
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result = []
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def preOrder(root):
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"""
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前序遍历二叉树
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"""
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if root is None:
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return
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# 访问优先级:根结点 -> 左子树 -> 右子树
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result.append(root.val)
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preOrder(root=root.left)
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preOrder(root=root.right)
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def inOrder(root):
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"""
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中序遍历二叉树
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"""
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if root is None:
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return
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# 访问优先级:左子树 -> 根结点 -> 右子树
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inOrder(root=root.left)
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result.append(root.val)
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inOrder(root=root.right)
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def postOrder(root):
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"""
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后序遍历二叉树
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"""
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if root is None:
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return
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# 访问优先级:左子树 -> 右子树 -> 根结点
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postOrder(root=root.left)
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postOrder(root=root.right)
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result.append(root.val)
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""" Driver Code """
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if __name__ == "__main__":
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# 初始化二叉树
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# 这里借助了一个从数组直接生成二叉树的函数
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root = list_to_tree(
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arr=[1, 2, 3, 4, 5, 6, 7, None, None, None, None, None, None, None, None]
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)
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print("\n初始化二叉树\n")
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print_tree(root)
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# 前序遍历
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result = []
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preOrder(root)
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print("\n前序遍历的结点打印序列 = ", result)
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assert result == [1, 2, 4, 5, 3, 6, 7]
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# 中序遍历
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result = []
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inOrder(root)
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print("\n中序遍历的结点打印序列 = ", result)
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assert result == [4, 2, 5, 1, 6, 3, 7]
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# 后序遍历
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result = []
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postOrder(root)
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print("\n后序遍历的结点打印序列 = ", result)
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assert result == [4, 5, 2, 6, 7, 3, 1]
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