N-ary Tree Preorder Traversal

最新推荐文章于 2022-04-20 03:28:39 发布

原创最新推荐文章于 2022-04-20 03:28:39 发布 · 205 阅读

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本文介绍了一个高效的N-ary树前序遍历算法实现，该算法在LeetCode上的运行速度超过69.62%的Java提交，并且内存使用率低于100%的Java提交。文章详细展示了算法的代码实现，包括如何递归地遍历树的节点。

/**
Runtime: 1 ms, faster than 69.62% of Java online submissions for N-ary Tree Preorder Traversal.

Memory Usage: 40.1 MB, less than 100.00% of Java online submissions for N-ary Tree Preorder Traversal.
*/
/*
// Definition for a Node.
class Node {
    public int val;
    public List<Node> children;

    public Node() {}

    public Node(int _val) {
        val = _val;
    }

    public Node(int _val, List<Node> _children) {
        val = _val;
        children = _children;
    }
};
*/

class Solution {
    public List<Integer> preorder(Node root) {
        if (root == null) {
            return new ArrayList<>();
        }
        ArrayList<Integer> result = new ArrayList<>();
        trace(root, result);
        return result;
    }
    private void trace(Node root, ArrayList<Integer> result) {
        if (root == null) {
              return;
        }
        result.add(root.val);
        if (root.children != null && root.children.size() != 0) {
            root.children.forEach(child -> trace(child, result));
        }
    }
}