Function nodeDepths

binary-trees/node-depths.js:10–25

(root)

// 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);