add node depths question

Author: betomoedano

binary-trees/node-depths.js

@@ -0,0 +1,37 @@
+// function nodeDepths(root, depth = 0) {
+//   if (root === null) return 0;
+//   return (
+//     depth + nodeDepths(root.left, depth + 1) + nodeDepths(root.right, depth + 1)
+//   );
+// }
+
+// O(n) time where n is the number of nodes
+// O(h) space where h is the height of the tree, because at most we are storing h items on the stack
+function nodeDepths(root) {
+  let sum = 0;
+  const stack = [{ node: root, depth: 0 }];
+
+  //DFS
+  while (stack.length > 0) {
+    const currentNode = stack.pop();
+    const { node, depth } = currentNode;
+
+    if (node === null) continue;
+    sum += depth;
+    stack.push({ node: node.left, depth: depth + 1 });
+    stack.push({ node: node.right, depth: depth + 1 });
+  }
+  return sum;
+}
+
+const root = new BinaryTree(1);
+root.left = new BinaryTree(2);
+root.left.left = new BinaryTree(4);
+root.left.left.left = new BinaryTree(8);
+root.left.left.right = new BinaryTree(9);
+root.left.right = new BinaryTree(5);
+root.right = new BinaryTree(3);
+root.right.left = new BinaryTree(6);
+root.right.right = new BinaryTree(7);
+
+console.log(nodeDepths(root));