Flatten Binary Tree to Linked List

最新推荐文章于 2022-09-06 16:04:14 发布

原创最新推荐文章于 2022-09-06 16:04:14 发布 · 1.5k 阅读

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二叉树 (binary tree) 专栏收录该内容

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本文介绍了一种将二叉树结构通过特定算法展平为链表的方法。该方法利用栈结构进行先序遍历，使得每个节点的右子节点指向下一个遍历到的节点，最终形成链表形式。

Given a binary tree, flatten it to a linked list in-place.

For example,
Given

The flattened tree should look like:

Hints:

If you notice carefully in the flattened tree, each node's right child points to the next node of a pre-order traversal.

/**
 * Definition for binary tree
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
public class Solution {
    public void flatten(TreeNode root) {
        if (root == null) return;
        Stack<TreeNode> stack = new Stack<TreeNode>();
        stack.push(root);
        TreeNode lastNode = null;
        while (!stack.isEmpty()) {
            TreeNode node = stack.pop();
            if (lastNode != null) {
                lastNode.left = null;
                lastNode.right = node;
            }
            lastNode = node;
            TreeNode left = node.left;
            TreeNode right = node.right;
            if (right != null) {
                stack.push(right);
            }
            if (left != null) {
                stack.push(left);
            }
        }
    }
}