题解 | #10.两个链表的第一个公共结点#

set遍历即可

function FindFirstCommonNode(pHead1, pHead2)
{
  let set = new Set();
  while(pHead1 != null){
    set.add(pHead1);
    pHead1 = pHead1.next;
  }
  
  while(pHead2 != null){
    if( set.has(pHead2) )  return pHead2;
    pHead2 = pHead2.next;
  }
  return null;
}

另一种方法，看题解就可以明白

function FindFirstCommonNode(pHead1, pHead2)
{
  let l1 = pHead1,
      l2 = pHead2;
  while(l1!=l2){
    l1 = l1!=null ? l1.next : pHead2;
    l2 = l2!=null ? l2.next : pHead1;
  }
  return l1;
}