At each node, the tree-visitor calls visit-node, our second function.

在每个节点处，tree - visitor都会调用我们的第二个函数visit - node。

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Compared with recursive algorithm for binary tree traversing, non-recursive algorithm reduces expenses of function calls, gains performance advantage.

二叉树遍历的非递归算法相对于递归算法，减少了函数调用等开销，具有性能优势。

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You can use the new derived tree node as a parameter to function calls.

生树节点可用作函数调用的参数。

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