返回类型数组的递归树遍历方法 [英] Recursive Tree Traversal Method With Return Type Array

问题描述

是否有一种方法可以递归遍历树并返回范围为该递归方法的数组?

Is there a way to recursively traverse a tree and return an array that is scoped to that recursive method?

因此，我最近回答了有关此主题的其他人的问题.可以在以下位置找到该问题: SO问题.我的解决方案在递归范围之外使用数组，因此该方法无法(或至少可能不应)返回数组.但是，有没有一种方法可以编写遍历树的递归方法，使其返回数组?即使编写一个调用递归方法的初始方法也可以，但是我想不出一种好方法.

So I recently answered someone else's question on this topic. That question can be found here: SO Question. My solution uses an array outside of the scope of the recursion, and therefore the method cannot (or at least probably should not) return the array. However, is there a way to write a recursive method for traversing trees such that it returns an array? Even writing an initial method that calls the recursive one would be fine, but I can't think of a good way to do this.

这是我之前建议的代码:

Here's the code that I suggested before:

private List nodeValues = new ArrayList();

public void traversePreRecursive(BinarySearchTreeNode node) 
{
    if (node != null)
    {
        nodeValues.add(node.getValue());
        traversePreRecursive(node.getLeft());
        traversePreRecursive(node.getRight());
    }
}

如您所见，ArrayList不在递归的范围之内-因此，返回它没有多大意义.有更好的方法吗?

As you can see the ArrayList is outside of the scope of the recursion - And therefore returning it doesn't make a lot of sense. Is there a better way to do this?

推荐答案

public static List traversePreRecursive(Node node) {
    if (node == null) return new ArrayList();

    List nodeValues = new ArrayList();
    nodeValues.add(node.getValue());
    nodeValues.addAll(traversePreRecursive(node.getLeft()));
    nodeValues.addAll(traversePreRecursive(node.getRight()));

    return nodeValues;
}

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