leetcode - Reverse Linked List @ Thu, Feb 23, 2023 9:10 PM
leetcode - Reverse Linked List @ Sun, Mar 5, 2023 9:43 PM
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function reverseList(head: ListNode | null): ListNode | null {

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function reverseList(head: ListNode | null): ListNode | null {

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  // base case, breaking recursive loop

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  // base case, breaking recursive loop

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  if (head === null || head.next === null) return head;

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  if (head === null || head.next === null) return head;

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  // head.next.next.next 到 base case, 即最后一个节点(倒数第一个)

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  const newHead = reverseList(head.next);

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  const newHead = reverseList(head.next);

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  // 由于是递归，函数栈一直增加，FILO 其实是从后往前处理的。最后处理第一个节点。

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  head.next.next = head;

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  head.next.next = head;

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  head.next = null;

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  head.next = null;

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  return newHead;

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  return newHead;

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function reverseList(head: ListNode | null): ListNode | null {

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function reverseList(head: ListNode | null): ListNode | null {

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  let prev = null;

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  let prev = null;

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  let cur = head;

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  let cur = head;

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  // 从头开始处理

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  while (cur !== null) {

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  while (cur !== null) {

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    // 把 next node 存起来

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    const next = cur.next;

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    const next = cur.next;

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    // 按顺序处理 node，把处理过的加到当前处理 node 的 next 指针上

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    cur.next = prev;

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    cur.next = prev;

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    // 处理完成的挂到 prev 变量上

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    prev = cur;

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    prev = cur;

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    // 接下来要处理的，进入下一次循环

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    cur = next;

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    cur = next;

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  }

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  }

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  return prev;

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  return prev;

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