python 平衡二叉树实现代码示例

 # -*- coding:utf-8 -*- # 日期：2018/6/12 8:37 # Author:小鼠标 # 节点对象 class Node: def __init__(self): self.left_children = None self.left_height = 0 self.right_children = None self.right_height = 0 self.value = None # 二叉树对象 class tree: def __init__(self): self.root = False self.front_list = [] self.middle_list = [] self.after_list = [] # 生成二叉树 def create_tree(self,n=0,l=[]): if l == []: print("传入的列表为空") return if n > len(l)-1: print("二叉树生成") return node = Node() node.value = l[n] if not self.root: self.root = node self.list = l else: self.add(self.root,node) self.create_tree(n+1,l) # 添加节点 def add(self,parent,new_node): if new_node.value > parent.value: # 插入值比父亲值大，所以在父节点右边 if parent.right_children == None: parent.right_children = new_node # 新插入节点的父亲节点的高度值为1，也就是子高度值0+1 parent.right_height = 1 # 插入值后 从下到上更新节点的height else: self.add(parent.right_children,new_node) # 父亲节点的右高度等于右孩子，左右高度中较大的值 + 1 parent.right_height = max(parent.right_children.right_height, parent.right_children.left_height) + 1 # ======= 此处开始判断平衡二叉树======= # 右边高度大于左边高度 属于右偏 if parent.right_height - parent.left_height >= 2: self.right_avertence(parent) else: # 插入值比父亲值小，所以在父节点左边 if parent.left_children == None: parent.left_children = new_node parent.left_height = 1 else: self.add(parent.left_children,new_node) parent.left_height = max(parent.left_children.right_height, parent.left_children.left_height) + 1 # ======= 此处开始判断平衡二叉树======= # 左边高度大于右边高度 属于左偏 if parent.left_height - parent.right_height >= 2: self.left_avertence(parent) # 更新当前节点下的所有节点的高度 def update_height(self,node): # 初始化节点高度值为0 node.left_height = 0 node.right_height = 0 # 是否到最底层的一个 if node.left_children == None and node.right_children == None: return else: if node.left_children: self.update_height(node.left_children) # 当前节点的高度等于左右子节点高度的较大值 + 1 node.left_height = max(node.left_children.left_height,node.left_children.right_height) + 1 if node.right_children: self.update_height(node.right_children) # 当前节点的高度等于左右子节点高度的较大值 + 1 node.right_height = max(node.right_children.left_height, node.right_children.right_height) + 1 # 检查是否仍有不平衡 if node.left_height - node.right_height >= 2: self.left_avertence(node) elif node.left_height - node.right_height <= -2: self.right_avertence(node) def right_avertence(self,node): # 右偏 就将当前节点的最左节点做父亲 new_code = Node() new_code.value = node.value new_code.left_children = node.left_children best_left = self.best_left_right(node.right_children) v = node.value # 返回的对象本身, if best_left == node.right_children and best_left.left_children == None: # 说明当前节点没有有节点 node.value = best_left.value node.right_children = best_left.right_children else: node.value = best_left.left_children.value best_left.left_children = best_left.left_children.right_children node.left_children = new_code self.update_height(node) # 处理左偏情况 def left_avertence(self,node): new_code = Node() new_code.value = node.value new_code.right_children = node.right_children best_right = self.best_left_right(node.left_children,1) v = node.value # 返回的对象本身, if best_right == node.left_children and best_right.right_children == None: # 说明当前节点没有有节点 node.value = best_right.value node.left_children = best_right.left_children else: node.value = best_right.right_children.value best_right.right_children = best_right.right_children.left_children node.right_children = new_code self.update_height(node) # 返回node节点最左（右）子孙的父级 def best_left_right(self,node,type=0): # type=0 默认找最左子孙 if type == 0: if node.left_children == None: return node elif node.left_children.left_children == None: return node else: return self.best_left_right(node.left_children,type) else: if node.right_children == None: return node elif node.right_children.right_children == None: return node else: return self.best_left_right(node.right_children,type) # 前序(先中再左最后右) def front(self,node=None): if node == None: self.front_list = [] node = self.root # 输出当前节点 self.front_list.append(node.value) # 先判断左枝 if not node.left_children == None: self.front(node.left_children) # 再判断右枝 if not node.right_children == None: self.front(node.right_children) # 返回最终结果 return self.front_list # 中序(先左再中最后右) def middle(self,node=None): if node == None: node = self.root # 先判断左枝 if not node.left_children == None: self.middle(node.left_children) # 输出当前节点 self.middle_list.append(node.value) # 再判断右枝 if not node.right_children == None: self.middle(node.right_children) return self.middle_list # 后序(先左再右最后中) def after(self,node=None): if node == None: node = self.root # 先判断左枝 if not node.left_children == None: self.after(node.left_children) # 再判断右枝 if not node.right_children == None: self.after(node.right_children) self.after_list.append(node.value) return self.after_list # 节点删除 def del_node(self,v,node=None): if node == None: node = self.root # 删除根节点 if node.value == v: self.del_root(self.root) return # 删除当前节点的左节点 if node.left_children: if node.left_children.value == v: self.del_left(node) return # 删除当前节点的右节点 if node.right_children: if node.right_children.value == v: self.del_right(node) return if v > node.value: if node.right_children: self.del_node(v, node.right_children) else: print("删除的元素不存在") else: if node.left_children: self.del_node(v, node.left_children) else: print("删除的元素不存在") #删除当前节点的右节点 def del_right(self,node): # 情况1 删除节点没有右枝 if node.right_children.right_children == None: node.right_children = node.right_children.left_children else: best_left = self.best_left_right(node.right_children.right_children) # 表示右枝最左孙就是右枝本身 if best_left == node.right_children.right_children and best_left.left_children == None: node.right_children.value = best_left.value node.right_children.right_children = best_left.right_children else: node.right_children.value = best_left.left_children.value best_left.left_children = best_left.left_children.right_children # 删除当前节点的左节点 def del_left(self,node): # 情况1 删除节点没有右枝 if node.left_children.right_children == None: node.left_children = node.left_children.left_children else: best_left = self.best_left_right(node.left_children.right_children) # 表示右枝最左子孙就是右枝本身 if best_left == node.left_children.right_children and best_left.left_children == None: node.left_children.value = best_left.value node.left_children.right_children = best_left.right_children else: node.left_children.value = best_left.left_children.value best_left.left_children = best_left.left_children.right_children # 删除根节点 def del_root(self,node): if node.right_children == None: if node.left_children == None: node.value = None else: self.root = node.left_children else: best_left = self.best_left_right(node.right_children) # 表示右枝最左子孙就是右枝本身 if best_left == node.right_children and best_left.left_children == None: node.value = best_left.value node.right_children = best_left.right_children else: node.value = best_left.left_children.value best_left.left_children = best_left.left_children.right_children # 搜索 def search(self,v,node=None): if node == None: node = self.root if node.value == v: return True if v > node.value: if not node.right_children == None: return self.search(v, node.right_children) else: if not node.left_children == None: return self.search(v, node.left_children) return False if __name__ == '__main__': # 需要建立二叉树的列表 list = [4, 6, 3, 1, 7, 9, 8, 5, 2] t = tree() t.create_tree(0,list) res = t.front() print('前序', res)