Java二维数组分别按照二叉树先序\中序\后序打印所有的节点输出

题目描述

分别按照二叉树先序&＃xff0c;中序和后序打印所有的节点。

示例1

输入

{1,2,3}

输出

[[1,2,3],[2,1,3],[2,3,1]]

import java.util.*;/** public class TreeNode {* int val &＃61; 0;* TreeNode left &＃61; null;* TreeNode right &＃61; null;* }*/public class Solution {private int preIndex &＃61; 0;private int midIndex &＃61; 0;private int lastIndex &＃61; 0;/*** * &＃64;param root TreeNode类 the root of binary tree* &＃64;return int整型二维数组*/public int[][] threeOrders (TreeNode root) {int treeNodesNum &＃61; getTotalTreeNodeNum(root);//因为就前、中、后 输出 所以就相当于{{前},{中},{后}}//treeNodesNum 算出整棵树的节点个数int[][] result &＃61; new int[3][treeNodesNum];pre(root,result);mid(root,result);last(root,result);return result;}public int getTotalTreeNodeNum(TreeNode root){if(root &＃61;&＃61; null){return 0;}return 1 &＃43; getTotalTreeNodeNum(root.left) &＃43; getTotalTreeNodeNum(root.right);}public void pre(TreeNode root,int[][] result){if(root &＃61;&＃61; null){return;}result[0][preIndex&＃43;&＃43;] &＃61; root.val;pre(root.left,result);pre(root.right,result);}public void mid(TreeNode root,int[][] result){if(root &＃61;&＃61; null){return;}mid(root.left,result);result[1][midIndex&＃43;&＃43;] &＃61; root.val;mid(root.right,result);}public void last(TreeNode root,int[][] result){if(root &＃61;&＃61; null){return;}last(root.left,result);last(root.right,result);result[2][lastIndex&＃43;&＃43;] &＃61; root.val; }
}