Populating Next Right Pointers in Each Node

最新推荐文章于 2022-04-05 16:12:16 发布

最新推荐文章于 2022-04-05 16:12:16 发布 · 58 阅读

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本文介绍了一种常数额外空间的方法来填充给定完美二叉树节点的下一个右指针，实现从左到右遍历树的顺序。

Given a binary tree

    struct TreeLinkNode {
      TreeLinkNode *left;
      TreeLinkNode *right;
      TreeLinkNode *next;
    }

Populate each next pointer to point to its next right node. If there is no next right node, the next pointer should be set to NULL.

Initially, all next pointers are set to NULL.

Note:

You may only use constant extra space.
You may assume that it is a perfect binary tree (ie, all leaves are at the same level, and every parent has two children).

For example,
Given the following perfect binary tree,

After calling your function, the tree should look like:

1 -> NULL
       /  \
      2 -> 3 -> NULL
     / \  / \
    4->5->6->7 -> NULL

/**
 * Definition for binary tree with next pointer.
 * public class TreeLinkNode {
 *     int val;
 *     TreeLinkNode left, right, next;
 *     TreeLinkNode(int x) { val = x; }
 * }
 */
public class Solution {
    public void connect(TreeLinkNode root) {
        if (root == null) {
        	return;
        }
        if (root.left != null) {
        	root.left.next = root.right;
        }
        if (root.right != null) {
        	if (root.next != null) {
        		root.right.next = root.next.left;
        	} else {
        		root.right.next = null;
        	}
        }
        connect(root.left);
        connect(root.right);
    }
}