反转链表-简单

难度：简单

题目描述：
反转一个单链表。

示例：

输入: 1->2->3->4->5->NULL
输出: 5->4->3->2->1->NULL

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题目解析：
递归： ```javascript var reverseList = function(head) { if(!head || !head.next) return head var next = head.next // 递归反转 var reverseHead = reverseList(next) // 变更指针 next.next = head head.next = null return reverseHead }; ```

循环：

var reverseList = function (head) {
  if (!head || !head.next) return head;
  var prev = null,
    curr = head;
  while (curr) {
    // 用于临时存储 curr 后继节点
    var next = curr.next;
    // 反转 curr 的后继指针
    curr.next = prev;
    // 变更prev、curr
    // 待反转节点指向下一个节点
    prev = curr;
    curr = next;
  }
  head = prev;
  return head;
};

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尾递归

var reverseList = function (head) {
  if (!head || !head.next) return head;
  head = reverse(null, head);
  return head;
};

var reverse = function (prev, curr) {
  if (!curr) return prev;
  var next = curr.next;
  curr.next = prev;
  return reverse(curr, next);
};

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# 反转链表-简单

反转链表-简单