链表

双指针

83. 删除排序链表中的重复元素

快慢指针

/**
 * v1 双指针（快慢指针）
 * @param {ListNode} head
 * @return {ListNode}
 */
let deleteDuplicates = function (head) {
  if (head === null) return null;
  let slow = head;
  let fast = head;
  while (fast !== null) {
    if (fast.val !== slow.val) {
      slow.next = fast;
      slow = slow.next;
    }
    fast = fast.next;
  }
  // 断开与后面重复元素的连接
  slow.next = null;
  return head;
};