full binary tree 是什么？

你可能下意识地以为 full binary tree 就是 满二叉树，毕竟直译过来就是如此，但事实并非如此。

以下内容来自 wikipedia：

• A full binary tree (sometimes referred to as a proper, plane, or strict binary tree) is a tree in which every node has either 0 or 2 children.
• A perfect binary tree is a binary tree in which all interior nodes have two children and all leaves have the same depth or same level (the level of a node defined as the number of edges or links from the root node to a node). A perfect binary tree is a full binary tree.
• A complete binary tree is a binary tree in which every level, except possibly the last, is completely filled, and all nodes in the last level are as far left as possible.

简而言之，在中文语境下：

• 满二叉树：perfect binary tree
• 完全二叉树：complete binary tree

而 full binary tree 是一个 “严格二叉树”。