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12-123

Language/Type: C++ linked lists pointers

Write the code that will produce the given "after" result from the given "before" starting point by modifying links between the nodes shown and/or creating new nodes as needed. Assume that the nodes have already been declared and initialized to match the "before" figure below. There may be more than one way to write the code, but do NOT change any existing node's data field value.

If a variable does not appear in the "after" picture, it doesn't matter what value it has after the changes are made. If a given node object does not appear in the "After" picture, you must free its memory to avoid a memory leak.

Before 
list: 1 -> 2 /
After 
list: 1 -> 2 -> 3 /

Assume that you are using the following ListNode structure: 

struct ListNode {
    int data;        // data stored in this node
    ListNode* next;  // a link to the next node in the list

    ListNode(int data = 0, ListNode* next = nullptr) { ... }   // constructor
};
Bare code. Write a fragment of C++ code as described, without any main function or heading around your code.

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