From b8e22ebe39acb6d5b0c482cd052036a1ac7e1fc2 Mon Sep 17 00:00:00 2001 From: Jawakar Sri <118127168+jawakarsri@users.noreply.github.com> Date: Tue, 1 Oct 2024 10:39:14 +0530 Subject: [PATCH] Create Copy List with Random Pointer --- .../Linked List/Copy List with Random Pointer | 94 +++++++++++++++++++ 1 file changed, 94 insertions(+) create mode 100644 Java/Linked List/Copy List with Random Pointer diff --git a/Java/Linked List/Copy List with Random Pointer b/Java/Linked List/Copy List with Random Pointer new file mode 100644 index 00000000..c06e5778 --- /dev/null +++ b/Java/Linked List/Copy List with Random Pointer @@ -0,0 +1,94 @@ +// Author: Jawakar Sri +// Date Created: 01/10/2024 +// Title: LeetCode Problem - Copy List with Random Pointer +// Problem Link: https://leetcode.com/problems/copy-list-with-random-pointer/ + +// Definition for a Node. +class Node { + int val; + Node next; + Node random; + public Node(int val) { + this.val = val; + this.next = null; + this.random = null; + } +} + +// Solution 1: Using extra space (HashMap) +class SolutionUsingHashMap { + public Node copyRandomList(Node head) { + if (head == null) return null; + + Node curr = head, newHead = new Node(0); + Node newCurr = newHead; + HashMap map = new HashMap(); + + // First pass: Create new nodes and store them in the map + while (curr != null) { + if (!map.containsKey(curr)) { + newCurr.next = new Node(curr.val); + map.put(curr, newCurr.next); + } else { + newCurr.next = map.get(curr); + } + + newCurr = newCurr.next; + + // Create random pointers + if (curr.random != null) { + if (!map.containsKey(curr.random)) { + newCurr.random = new Node(curr.random.val); + map.put(curr.random, newCurr.random); + } else { + newCurr.random = map.get(curr.random); + } + } + + curr = curr.next; + } + + return newHead.next; + } +} + +// Solution 2: Constant space (In-place modification) +class SolutionUsingInPlace { + public Node copyRandomList(Node head) { + if (head == null) return null; + + Node curr = head; + + // Step 1: Create a new node for each original node and link them in place + while (curr != null) { + Node next = curr.next; + curr.next = new Node(curr.val); + curr.next.next = next; + curr = next; + } + + // Step 2: Set random pointers for the copied nodes + curr = head; + while (curr != null) { + if (curr.random != null) { + curr.next.random = curr.random.next; + } + curr = curr.next.next; + } + + // Step 3: Separate the original and copied lists + curr = head; + Node newHead = new Node(0); // Dummy node + Node newCurr = newHead; + + while (curr != null) { + Node next = curr.next.next; + newCurr.next = curr.next; + newCurr = newCurr.next; + curr.next = next; + curr = next; + } + + return newHead.next; + } +} pFad - Phonifier reborn

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