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链表中倒数第 k 个节点

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题目类型: 链表, 快慢指针

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题目​

给定一个链表, 找到该链表倒数第 k 个节点.

示例

输入: 1->2->3->4->5->NULL, k = 2

输出: 4->5->NULL

题解​

让快指针先走 k 步, 再快慢指针往前一起走, 快指针走到头了, 慢指针就指向了链表中倒数第 k 个节点.

/**
 * Definition for singly-linked list.
 * function ListNode(val) {
 *     this.val = val;
 *     this.next = null;
 * }
 */
/**
 * @param {ListNode} head
 * @param {number} k
 * @return {ListNode}
 */
var getKthFromEnd = function (head, k) {
  let fast = head,
    slow = head

  while (k > 0) {
    fast = fast.next
    k--
  }

  while (fast) {
    fast = fast.next
    slow = slow.next
  }

  return slow
}