链表

/**
 * Definition for singly-linked list.
 * function ListNode(val, next) {
 *     this.val = (val===undefined ? 0 : val)
 *     this.next = (next===undefined ? null : next)
 * }
 */
/**
 * @param {ListNode} head
 * @return {ListNode}
 */
var deleteDuplicates = function (head) {
  if (!head) return head;
  let current = head;

  while (current.next) {
    if (current.val === current.next.val) {
      current.next = current.next.next;
    } else {
      current = current.next;
    }
  }
  return head;
};

206. 反转链表(简单)

迭代方式


/**
 * Definition for singly-linked list.
 * function ListNode(val, next) {
 *     this.val = (val===undefined ? 0 : val)
 *     this.next = (next===undefined ? null : next)
 * }
 */
/**
 * @param {ListNode} head
 * @return {ListNode}
 */
var reverseList = function (head) {
  let preCurrent = null
  let next = null
  while (head) {
      next = head.next

      head.next = preCurrent
      preCurrent = head

      head = next
  }
  return preCurrent
};

头插法

1.定义一个新的头节点 2.依次将节点插入新头节点与第一个节点之间

/**
 * Definition for singly-linked list.
 * function ListNode(val, next) {
 *     this.val = (val===undefined ? 0 : val)
 *     this.next = (next===undefined ? null : next)
 * }
 */
/**
 * @param {ListNode} head
 * @return {ListNode}
 */
var reverseList = function (head) {
  // 定义一个新链表
  let temp = new ListNode();
  let next = null;
  while (head) {
    next = head.next;
    // 旧链表一个个插入到新链表头尾中间
    head.next = temp.next;
    temp.next = head;

    head = next;
  }
  return temp.next;
};

19. 删除链表的倒数第 N 个结点(简单)

/**
 * Definition for singly-linked list.
 * function ListNode(val, next) {
 *     this.val = (val===undefined ? 0 : val)
 *     this.next = (next===undefined ? null : next)
 * }
 */
/**
 * @param {ListNode} head
 * @param {number} n
 * @return {ListNode}
 */
var removeNthFromEnd = function (head, n) {
  // 获取链表长度
  let listLength = 0
  let node = head
  while (node) {
    listLength++
    node = node.next
  }
  // 删除的节点的index
  let deleteNodeIndex = listLength - n
  // 边界处理：头部删除的时候直接返回head.next
  if (deleteNodeIndex === 0) return head.next

  // 注意得复制节点出来遍历，因为等下要返回头部head
  node = head
  let lastNode = null
  while (deleteNodeIndex > 0) {
    lastNode = node
    node = node.next
    deleteNodeIndex--
  }
  lastNode.next = node.next
  return head
};

链表#

链表