数据结构-二叉树

class Node(object):
    def __init__(self,item):
        self.item = item
        self.child1 = None
        self.child2 = None
 
class Tree(object):
    def __init__(self):
        self.root = None
 
    def add(self, item):
        node = Node(item)
        if self.root is None:
            self.root = node
        else:
            q = [self.root]
 
            while True:
                pop_node = q.pop(0)
                if pop_node.child1 is None:
                    pop_node.child1 = node
                    return
                elif pop_node.child2 is None:
                    pop_node.child2 = node
                    return
                else:
                    q.append(pop_node.child1)
                    q.append(pop_node.child2)
 
    def traverse(self):  # 层次遍历
        if self.root is None:
            return None
        q = [self.root]
        res = [self.root.item]
        while q != []:
            pop_node = q.pop(0)
            if pop_node.child1 is not None:
                q.append(pop_node.child1)
                res.append(pop_node.child1.item)
 
            if pop_node.child2 is not None:
                q.append(pop_node.child2)
                res.append(pop_node.child2.item)
        return res
 
    def preorder(self,root):  # 先序遍历
        if root is None:
            return []
        result = [root.item]
        left_item = self.preorder(root.child1)
        right_item = self.preorder(root.child2)
        return result + left_item + right_item
 
    def inorder(self,root):  # 中序序遍历
        if root is None:
            return []
        result = [root.item]
        left_item = self.inorder(root.child1)
        right_item = self.inorder(root.child2)
        return left_item + result + right_item
 
    def postorder(self,root):  # 后序遍历
        if root is None:
            return []
        result = [root.item]
        left_item = self.postorder(root.child1)
        right_item = self.postorder(root.child2)
        return left_item + right_item + result
if __name__ == "__main__":
    
    t = Tree()
    for i in range(10):
        t.add(i)
    print('层序遍历:',t.traverse())
    print('先序遍历:',t.preorder(t.root))
    print('中序遍历:',t.inorder(t.root))
    print('后序遍历:',t.postorder(t.root))

层序遍历: [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
先序遍历: [0, 1, 3, 7, 8, 4, 9, 2, 5, 6]
中序遍历: [7, 3, 8, 1, 9, 4, 0, 5, 2, 6]
后序遍历: [7, 8, 3, 9, 4, 1, 5, 6, 2, 0]