Leetcode•May 28, 2025
Binary Tree Postorder Traversal
Hazrat Ali
Leetcode
Given the root of a binary tree, return the postorder traversal of its nodes' values.
Example 1:
Input: root = [1,null,2,3]
Output: [3,2,1]
Explanation:
Example 2:
Input: root = [1,2,3,4,5,null,8,null,null,6,7,9]
Output: [4,6,7,5,2,9,8,3,1]
Explanation:
Example 3:
Input: root = []
Output: []
Example 4:
Input: root = [1]
Output: [1]
Solution
/**
* @param {TreeNode} root
* @return {number[]}
*/
var postorderTraversal = function(root) {
if (!root) {
return [];
}
const result = [];
const stack = [root];
while (stack.length) {
const node = stack.pop();
result.unshift(node.val);
if (node.left) {
stack.push(node.left);
}
if (node.right) {
stack.push(node.right);
}
}
return result;
};