Title description
Print all nodes according to binary tree first order, middle order and post order respectively.
import java.util.*;
/*
* public class TreeNode {
* int val = 0;
* TreeNode left = null;
* TreeNode right = null;
* }
*/
public class Solution {
/**
*
* @param root TreeNode类 the root of binary tree
* @return int整型二维数组
*/
// 用list集合存储元素
List<Integer> pre = new ArrayList<>();
List<Integer> mid = new ArrayList<>();
List<Integer> nex = new ArrayList<>();
public int[][] threeOrders(TreeNode root) {
// write code here
preOrder(root);
midOrder(root);
nexOrder(root);
int len = pre.size();
int[][] arr = new int[3][len];
for (int i = 0; i < len; i++) {
arr[0][i] = pre.get(i);
}
for (int i = 0; i < len; i++) {
arr[1][i] = mid.get(i);
}
for (int i = 0; i < len; i++) {
arr[2][i] = nex.get(i);
}
return arr;
}
// 前序遍历
public void preOrder(TreeNode root) {
if (root != null) {
pre.add(root.val);
preOrder(root.left);
preOrder(root.right);
}
}
// 中序遍历
public void midOrder(TreeNode root) {
if (root != null) {
midOrder(root.left);
mid.add(root.val);
midOrder(root.right);
}
}
// 后序遍历
public void nexOrder(TreeNode root) {
if (root != null) {
nexOrder(root.left);
nexOrder(root.right);
nex.add(root.val);
}
}
}