编辑代码

const findFirstNode = (nodeList) => {
    // TODO write your impl here
    // 拿到所有指向的指针
  if (!(nodeList && nodeList.length > 0)) {
    return '链表为空';
  }
  const nextIds = nodeList.map(n => n.nextId);
  const heads = nodeList.filter(n => !nextIds.include(n.id));
  if (heads.length === 0) {
    return '链表为环';
  }
  if (heads.length === 1) {
    return `头结点为：${JSON.stringify(heads[0])}`;
  }
  if (heads.length > 1) {
    return `头结点有多个，分别为：${heads.map(h => JSON.stringify(h)).join(',')}`;
  }
};