149 lines
3.8 KiB
JavaScript
149 lines
3.8 KiB
JavaScript
/**
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* https://leetcode.cn/problems/copy-list-with-random-pointer/?envType=study-plan-v2&envId=top-interview-150
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* // Definition for a _Node.
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* function _Node(val, next, random) {
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* this.val = val;
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* this.next = next;
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* this.random = random;
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* };
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*/
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/**
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* @param {_Node} head
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* @return {_Node}
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*/
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const copyRandomList = function (head) {
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};
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// Definition for a _Node.
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// eslint-disable-next-line no-underscore-dangle
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function _Node(val, next, random) {
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this.val = val;
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this.next = next;
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this.random = random;
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}
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/*
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遍历整个链表，创建每一个节点的克隆节点，并且使用map将它们直接联系起来，原节点作为key，新节点作为value,
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遍历完毕之后，再遍历一一遍原链表，根据random_index和map来为可能列表添加random_index
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*/
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function f1(head) {
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const map = new Map(); // 储存原链表和克隆链表直接的关系
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const dummyHead = new _Node(); // 哑节点，用于构建克隆链表
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let curClone = dummyHead;
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let cur = head;
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while (cur) {
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// 创建克隆节点
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curClone.next = new _Node(cur.val);
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curClone = curClone.next;
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// 将原节点和克隆节点映射
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map.set(cur, curClone);
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cur = cur.next;
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}
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// 遍历原节点，根据原节点的信息为克隆节点添加random指针
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cur = head;
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curClone = dummyHead.next;
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while (cur) {
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if (cur.random) {
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curClone.random = map.get(cur.random);
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}
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cur = cur.next;
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curClone = curClone.next;
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}
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return dummyHead.next;
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}
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/*
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f1 的优化版本，首先创建克隆节点和映射，之后再拼接克隆链表
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*/
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function f2(head) {
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if (!head) return null;
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const map = new Map(); // 储存原节点 => 克隆节点的映射
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let cur = head;
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// 第一次遍历：创建所有新节点，并放入 map 中
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while (cur) {
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map.set(cur, new _Node(cur.val));
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cur = cur.next;
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}
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cur = head;
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// 第二次遍历：设置新节点的 next 和 random 指针
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while (cur) {
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const cloneNode = map.get(cur);
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cloneNode.next = map.get(cur.next) || null;
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cloneNode.random = map.get(cur.random) || null;
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cur = cur.next;
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}
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return map.get(head);
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}
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/*
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直接再原节点中插入克隆节点，那么原节点和克隆节点就存在了引用关系，之后根据引用关系来设置random，最后
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分离原链表和克隆链表即可
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*/
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function f3(head) {
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if (!head) return null;
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// 创建克隆节点，并且把克隆节点放在原节点后面
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let cur = head;
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while (cur) {
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// 将原节点之后的所有节点移动到克隆节点的后面，再将克隆节点作为原节点的next
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const clone = new _Node(cur.val);
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clone.next = cur.next;
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cur.next = clone;
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cur = clone.next; // 遍历下一个原节点
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}
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// 更具原节点的random来设置克隆节点的random
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cur = head;
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while (cur) {
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if (cur.random) {
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cur.next.random = cur.random.next;
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}
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cur = cur.next.next; // 下一个原节点
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}
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// 分离节点
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cur = head;
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const cloneHead = head.next;
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while (cur) {
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const clone = cur.next;
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cur.next = clone.next; // 原节点指向原本下一个节点
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if (clone.next) {
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clone.next = clone.next.next; // 克隆节点指向克隆节点的下一个节点
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}
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cur = cur.next;
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}
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return cloneHead;
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}
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/*
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回溯加哈希表
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*/
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function f4(head, cacheMap = new Map()) {
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if (!head) return null;
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// 如果没有这个节点的克隆映射
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if (!cacheMap.has(head)) {
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const clone = new _Node(head.val);
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cacheMap.set(head, clone);
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// 克隆节点的下一个节点为当前节点的下一个节点的克隆节点，递归调用即可
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clone.next = f4(head.next, cacheMap);
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// random同理
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clone.random = f4(head.random, cacheMap);
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}
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// 如果有克隆节点，直接返回
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return cacheMap.get(head);
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}
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