leetcode-160 相交链表

/**
 * Definition for singly-linked list.
 * function ListNode(val) {
 *     this.val = val;
 *     this.next = null;
 * }
 */

/**
 * @param {ListNode} headA
 * @param {ListNode} headB
 * @return {ListNode}
 */
var getIntersectionNode = function(headA, headB) {
  const map = new WeakMap();
  let curA = headA, curB=headB;
  while(curA) {
    map.set(curA, true);
    curA = curA.next;
  }
  while(curB) {
    if (map.has(curB)) {
      return curB;
    }
    curB = curB.next;
  }
  return null;
};

/**
 * Definition for singly-linked list.
 * function ListNode(val) {
 *     this.val = val;
 *     this.next = null;
 * }
 */

/**
 * @param {ListNode} headA
 * @param {ListNode} headB
 * @return {ListNode}
 */
var getIntersectionNode = function (headA, headB) {
  let pA = headA,
    pB = headB;
  while (pA !== pB) {
    pA = pA ? pA.next : headB;
    pB = pB ? pB.next : headA;
  }
  return pA;
};