Leetcode 2、141：两数相加-环形链表

两数相加

  var addTwoNumbers = function (l1, l2) {

    let cur1 = l1;
    let cur2 = l2;
  
    let newLinkHead = new ListNode(0);
    let result = newLinkHead;
  
    let yu = 0; // 余数
    let carrybit = 0; // 进位
    let val1; 
    let val2;
    while (cur1 || cur2) {
      val1 = (cur1 && cur1.val) || 0;
      val2 = (cur2 && cur2.val) || 0;
  
      yu = (val1 + val2 + carrybit) % 10; 
  
      result.next = new ListNode(yu);
  
      if (val1 + val2 + carrybit >= 10) { 
        carrybit = 1;
      } else {
        carrybit = 0;
      }
  
      result = result.next;
      cur1 = cur1 && cur1.next;
      cur2 = cur2 && cur2.next;
  
    }

    if (carrybit >0) { // val1 + val2 + carrybit >= 10 
      result.next = new ListNode(carrybit);
    }
  
    return newLinkHead.next; 
  };

环形链表

var hasCycle = function (head) {
  if (!head) {
    return false
  }
  let pre = head;
  let cur = head;

  while (pre && pre.next) {
    pre = pre.next.next;
    cur = cur.next;
    if (pre == cur) {
      return true
    }
  }
  return false
}