Postorder Traversal
Practice postorder traversal (Left → Right → Root) with visual state, execution logs, and recursive trace output.
class TreeNode {
data: any;
left: TreeNode | null;
right: TreeNode | null;
}Add
Parent
Delete
Add parent: none | Delete target: none. Delete removes only the selected node and reconnects children.
Traverse
100%
Want to see how the recursive code works?
Copy this code and paste it in the Recursion Tracer to visualize the call stack step-by-step.
class TreeNode {
constructor(val) {
this.val = val;
this.left = null;
this.right = null;
}
}
function buildTree(arr) {
if (!arr.length || arr[0] === null) return null;
const root = new TreeNode(arr[0]);
const queue = [root];
let i = 1;
while (queue.length > 0 && i < arr.length) {
const node = queue.shift();
if (i < arr.length && arr[i] !== null) {
node.left = new TreeNode(arr[i]);
queue.push(node.left);
}
i++;
if (i < arr.length && arr[i] !== null) {
node.right = new TreeNode(arr[i]);
queue.push(node.right);
}
i++;
}
return root;
}
function postorder(node) {
if (!node) return [];
return [...postorder(node.left), ...postorder(node.right), node.val];
}
// Build and traverse
const input = [1, 2, 3, 4, 5, null, 6];
const root = buildTree(input);
console.log("Postorder:", postorder(root));