// DFS 풀이법
// 비교 연산 때문인지 속도가 느림
var maxDepth = function (root) {
  if (!root) return 0;

  root.depth = 1;
  const stack = [root];

  let depth = 1;

  while (stack.length) {
    const node = stack.pop();
    if (node.children) {
      [...node.children].forEach((childNode) => {
        childNode.depth = node.depth + 1;
        if (depth < childNode.depth) depth = childNode.depth;
        stack.push(childNode);
      });
    }
  }

  return depth;
};

// BFS 풀이법
// 최대값을 구하는 문제이므로 BFS가 더
var maxDepth = function (root) {
  if (!root) return 0;

  const stack = [root];

  let depth = 1;
  let children = 1;

  while (stack.length) {
    while (children) {
      const node = stack.shift();
      children--;

      if (node.children) stack.push(...node.children);
    }
    children = stack.length;
    depth++;
  }

  return --depth;
};

// children 변수를 만들 필요 없이, while문 내에서 stack.length를 활용하면 됐음.
var maxDepth = function (root) {
  if (!root) return 0;

  const stack = [root];

  let depth = 0;

  while (stack.length) {
    const children = stack.length;

    for (let i = 0; i < children; i++) {
      const node = stack.shift();
      if (node.children) stack.push(...node.children);
    }
    depth++;
  }

  return depth;
};