标签:public treenode array 数组 efi binary for integer level
给定一个二叉树,返回其节点值的锯齿形层次遍历。(即先从左往右,再从右往左进行下一层遍历,以此类推,层与层之间交替进行)。
例如:
给定二叉树 [3,9,20,null,null,15,7],
3
/ \
9 20
/ \
15 7
返回锯齿形层次遍历如下:
[
[3],
[20,9],
[15,7]
]
来源:力扣(LeetCode)
链接:https://leetcode-cn.com/problems/binary-tree-zigzag-level-order-traversal
/** * Definition for a binary tree node. * public class TreeNode { * int val; * TreeNode left; * TreeNode right; * TreeNode(int x) { val = x; } * } */ /* dfs遍历二叉树,从左至右。每个元素都有个deep(深度),只需将root.val放入result.get(deep)数组中即可。 时间复杂度O(n),击败97%用户。 */ class Solution { public static List<List<Integer>> result; public static void dfs(TreeNode root,int deep){ if(root.left == null && root.right == null)return; if(root.left!=null){ if(deep+1 > (result.size())-1)result.add(new LinkedList<Integer>()); if(deep%2!=0)result.get(deep+1).add(root.left.val); else result.get(deep+1).add(0,root.left.val); dfs(root.left,deep+1); } if(root.right!=null){ if(deep+1 > (result.size())-1)result.add(new LinkedList<Integer>()); if(deep%2!=0)result.get(deep+1).add(root.right.val); else result.get(deep+1).add(0,root.right.val); dfs(root.right,deep+1); } } public List<List<Integer>> zigzagLevelOrder(TreeNode root) { result = new ArrayList<List<Integer>>(); if(root == null)return result; result.add(new LinkedList<Integer>()); result.get(0).add(root.val); dfs(root,0); return result; } }
标签:public treenode array 数组 efi binary for integer level
原文地址:https://www.cnblogs.com/xxxxxiaochuan/p/13285298.html