LeetCode——Populating Next Right Pointers in Each Node

標籤：leetcode

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,

         1       /        2    3     / \  /     4  5  6  7

After calling your function, the tree should look like:

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

原題連結： https://oj.leetcode.com/problems/populating-next-right-pointers-in-each-node/

題目： 給定一個二叉樹(假設是完全二叉樹)，把每個節點的next指標指向其右側節點。

思路：首先想到的是，層序遍曆樹，在遍曆的同時添加節點對右側節點的指標。

另一種簡潔的方法是採用遞迴來實現，間單直觀。

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