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BinaryTreeInorderTraversal.java
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BinaryTreeInorderTraversal.java
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package algorithms;
import java.util.ArrayList;
import java.util.List;
import java.util.Stack;
/**
* 94. Binary Tree Inorder Traversal
* https://leetcode.com/problems/binary-tree-inorder-traversal/
* Difficulty : Medium
* Related Topics : HashTable, Stack, Tree
*
* Given a binary tree, return the inorder traversal of its nodes' values.
*
* Example:
*
* Input: [1,null,2,3]
* 1
* \
* 2
* /
* 3
*
* Output: [1,3,2]
*
* 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;
* }
* }
*
* created by cenkc on 8/12/2020
*/
public class BinaryTreeInorderTraversal {
// iterative
// Runtime: 1 ms, faster than 29.43% of Java online submissions for Binary Tree Inorder Traversal.
// Memory Usage: 39.4 MB, less than 5.05% of Java online submissions for Binary Tree Inorder Traversal.
public List<Integer> inorderTraversal(TreeNode root) {
List<Integer> result = new ArrayList<>();
if (root == null) return result;
Stack<TreeNode> s = new Stack<>();
while ( ! s.isEmpty() || root != null) {
if (root != null) {
s.push(root);
root = root.left;
} else {
root = s.pop();
result.add(root.val);
root = root.right;
}
}
return result;
}
/*
// recursive
// Runtime: 0 ms, faster than 100.00% of Java online submissions for Binary Tree Inorder Traversal.
// Memory Usage: 38 MB, less than 8.81% of Java online submissions for Binary Tree Inorder Traversal.
private List<Integer> result = new ArrayList<>();
public List<Integer> inorderTraversal(TreeNode root) {
if (root == null) return result;
inOrderTraverse(root);
return result;
}
private void inOrderTraverse(TreeNode node) {
if (node.left != null) inOrderTraverse(node.left);
if (node != null) result.add(node.val);
if (node.right != null) inOrderTraverse(node.right);
}
*/
}