java
TreeNode{
int val;
TreeNode left;
TreeNode right;
TreeNode(){}
TreeNode(int val){
this.val = val;
}
TreeNode(int val, TreeNode left, TreeNode right) {
this.val = val;
this.left = left;
this.right = right;
}
}
java
/**
* Definition for a binary tree node.
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode() {}
* TreeNode(int val) { this.val = val; }
* TreeNode(int val, TreeNode left, TreeNode right) {
* this.val = val;
* this.left = left;
* this.right = right;
* }
* }
*/
class Solution {
public List<Integer> preorderTraversal(TreeNode root) {
List<Integer> res = new ArrayList<>();
if (root == null) return res;
traversal(res, root);
return res;
}
private void traversal(List<Integer> res, TreeNode root) {
if (root == null) return;
res.add(root.val);
traversal(res, root.left);
traversal(res, root.right);
}
}
java
/**
* Definition for a binary tree node.
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode() {}
* TreeNode(int val) { this.val = val; }
* TreeNode(int val, TreeNode left, TreeNode right) {
* this.val = val;
* this.left = left;
* this.right = right;
* }
* }
*/
class Solution {
public List<Integer> postorderTraversal(TreeNode root) {
List<Integer> res = new ArrayList<>();
if (root == null) return res;
traversal(res, root);
return res;
}
private void traversal(List<Integer> res, TreeNode root) {
if (root == null) return;
traversal(res, root.left);
traversal(res, root.right);
res.add(root.val);
}
}
java
/**
* Definition for a binary tree node.
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode() {}
* TreeNode(int val) { this.val = val; }
* TreeNode(int val, TreeNode left, TreeNode right) {
* this.val = val;
* this.left = left;
* this.right = right;
* }
* }
*/
class Solution {
public List<Integer> inorderTraversal(TreeNode root) {
List<Integer> res = new ArrayList<>();
if (root == null) return res;
traversal(res, root);
return res;
}
private void traversal(List<Integer> res, TreeNode root) {
if (root == null) return;
traversal(res, root.left);
res.add(root.val);
traversal(res, root.right);
}
}