add binary_tree and avl_tree python code

codes/python/chapter_tree/binary_search_tree.py

@@ -1,10 +1,173 @@
-'''
+"""
 File: binary_search_tree.py
 Created Time: 2022-11-25
 Author: Krahets (krahets@163.com)
-'''
+"""
 
 import sys, os.path as osp
+
 sys.path.append(osp.dirname(osp.dirname(osp.abspath(__file__))))
 from include import *
 
+
+class BinarySearchTree:
+    """
+    二叉搜索树
+    """
+
+    def __init__(self, nums) -> None:
+        nums.sort()
+        self.__root = self.buildTree(nums, 0, len(nums) - 1)
+
+    def buildTree(self, nums, start_index, end_index):
+        if start_index > end_index:
+            return None
+        mid = (start_index + end_index) // 2
+        root = TreeNode(nums[mid])
+        root.left = self.buildTree(
+            nums=nums, start_index=start_index, end_index=mid - 1
+        )
+        root.right = self.buildTree(nums=nums, start_index=mid + 1, end_index=end_index)
+        return root
+
+    def get_root(self):
+        return self.__root
+
+    def search(self, num):
+        """
+        查找结点
+        """
+        cur = self.get_root()
+        # 循环查找，越过叶结点后跳出
+        while cur is not None:
+            # 目标结点在 root 的右子树中
+            if cur.val < num:
+                cur = cur.right
+            # 目标结点在 root 的左子树中
+            elif cur.val > num:
+                cur = cur.left
+            # 找到目标结点，跳出循环
+            else:
+                break
+        return cur
+
+    def insert(self, num):
+        """
+        插入结点
+        """
+        root = self.get_root()
+        # 若树为空，直接提前返回
+        if root is None:
+            return None
+
+        cur = root
+        pre = None
+
+        # 循环查找，越过叶结点后跳出
+        while cur is not None:
+            # 找到重复结点，直接返回
+            if cur.val == num:
+                return None
+            pre = cur
+
+            if cur.val < num:  # 插入位置在 root 的右子树中
+                cur = cur.right
+            else:  # 插入位置在 root 的左子树中
+                cur = cur.left
+
+        # 插入结点 val
+        node = TreeNode(num)
+        if pre.val < num:
+            pre.right = node
+        else:
+            pre.left = node
+        return node
+
+    def remove(self, num):
+        """
+        删除结点
+        """
+        root = self.get_root()
+        # 若树为空，直接提前返回
+        if root is None:
+            return None
+
+        cur = root
+        pre = None
+
+        # 循环查找，越过叶结点后跳出
+        while cur is not None:
+            # 找到待删除结点，跳出循环
+            if cur.val == num:
+                break
+            pre = cur
+            if cur.val < num:  # 待删除结点在 root 的右子树中
+                cur = cur.right
+            else:  # 待删除结点在 root 的左子树中
+                cur = cur.left
+
+        # 若无待删除结点，则直接返回
+        if cur is None:
+            return None
+
+        # 子结点数量 = 0 or 1
+        if cur.left is None or cur.right is None:
+            # 当子结点数量 = 0 / 1 时， child = null / 该子结点
+            child = cur.left or cur.right
+            # 删除结点 cur
+            if pre.left == cur:
+                pre.left = child
+            else:
+                pre.right = child
+        # 子结点数量 = 2
+        else:
+            # 获取中序遍历中 cur 的下一个结点
+            nex = self.min(cur.right)
+            tmp = nex.val
+            # 递归删除结点 nex
+            self.remove(nex.val)
+            # 将 nex 的值复制给 cur
+            cur.val = tmp
+        return cur
+
+    def min(self, root):
+        """
+        获取最小结点
+        """
+        if root is None:
+            return root
+
+        # 循环访问左子结点，直到叶结点时为最小结点，跳出
+        while root.left is not None:
+            root = root.left
+        return root
+
+
+if __name__ == "__main__":
+    # 初始化二叉搜索树
+    nums = list(range(1, 16))
+    bst = BinarySearchTree(nums=nums)
+    print("\n初始化的二叉树为\n")
+    print_tree(bst.get_root())
+
+    # 查找结点
+    node = bst.search(5)
+    print("\n查找到的结点对象为: {}，结点值 = {}".format(node, node.val))
+
+    # 插入结点
+    ndoe = bst.insert(16)
+    print("\n插入结点 16 后，二叉树为\n")
+    print_tree(bst.get_root())
+
+    # 删除结点
+    bst.remove(1)
+    print("\n删除结点 1 后，二叉树为\n")
+    print_tree(bst.get_root())
+
+    bst.remove(2)
+    print("\n删除结点 2 后，二叉树为\n")
+    print_tree(bst.get_root())
+
+    bst.remove(4)
+    print("\n删除结点 4 后，二叉树为\n")
+    print_tree(bst.get_root())