僅用於自己學習記錄

二叉樹

class Node:
    def __init__(self, item):
        self.elem = item
        self.lchild = None
        self.rchild = None```


class Binary_tree:
    def __init__(self, node=None):
        self.root = node

    def add(self, item):
        '''從上到下，從左到右新增元素,逐層查詢遍歷空值'''
        node = Node(item)
        if self.root is None:
            self.root = node
            return
        queue = [self.root]
        while queue:
            n = queue.pop(0)
            if n.lchild is None:
                n.lchild = node
                return
            else:
                queue.append(n.lchild)
            if n.rchild is None:
                n.rchild = node
                return
            else:
                queue.append(n.rchild)

    def breath_travel(self):
        '''廣度優先遍歷，逐層從左到右'''
        if self.root is None:
            return
        queue = [self.root]
        while queue:
            n = queue.pop(0)
            print(n.elem)
            if n.lchild:
                queue.append(n.lchild)
            if n.rchild:
                queue.append(n.rchild)

    def preorder(self, node=None):
        '''先序遍歷'''
        if node is None:
            return
        print(node.elem,end=' ')
        self.preorder(node.lchild)
        self.preorder(node.rchild)

    def inorder(self,node):
        '''中序遍歷'''
        if node is None:
            return
        self.inorder(node.lchild)
        print(node.elem,end=' ')
        self.inorder(node.rchild)

    def postorder(self,node):
        '''後序遍歷'''
        if node is None:
            return
        self.postorder(node.lchild)
        self.postorder(node.rchild)
        print(node.elem,end=' ')

```if __name__ == '__main__':
    binary_tree = Binary_tree()
    binary_tree.add(0)
    binary_tree.add(1)
    binary_tree.add(2)
    binary_tree.add(3)
    binary_tree.add(4)
    binary_tree.add(5)
    binary_tree.add(6)
    binary_tree.add(7)
    binary_tree.add(8)
    binary_tree.add(9)
    binary_tree.add(10)
    binary_tree.breath_travel()
    binary_tree.preorder(binary_tree.root)
    print(' ')
    binary_tree.inorder(binary_tree.root)
    print(' ')
    binary_tree.postorder(binary_tree.root)```
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