leetcode -reverseLinkedList

Leetcode题解之 —— 反转链表

思路

---

思路一: 转化为数组

• 利用reverse反转

思路二: 双指针迭代

• prev指针存储上一个节点
• current迭代循环

题解

---

数组法:

/**
 * @param {ListNode} head
 * @return {ListNode}
 */
var reverseList = function(head) {
  // TODO solution 1
  const cache = [];
  let current = head;

  while (current) {
    cache.push(new ListNode(current.val));
    current = current.next;
  }

  if (!cache.length) {
    return null;
  }

  cache.reverse();

  for (const [index, node] of cache.entries()) {
    node.next = cache[index + 1];
  }

  return cache[0];
};

双指针法:

/**
 * @param {ListNode} head
 * @return {ListNode}
 */
var reverseList = function(head) {
  let prev = null;
  let current = head;

  while (current) {
    const next = current.next;
    current.next = prev;
    prev = current;
    current = next;
  }

  return prev;
};