Java Algorithms: Copying List with Random Pointer (LeetCode)

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A linked list of length n is given such that each node contains an additional random pointer, which could point to any node in the list, or null.
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Let’s start from solving the first subproblem. Let’s do simple thing iterate through linked list and create a copy for every node in it. I choose HashMap for storing pairs like old node -> new node. As long as we’re going to iterate from head of the list to tail let’s also introduce temp variable and set it to be the head of the list.