Create a Doubly Linked List from a Ternary Tree
Given a ternary tree, create a doubly linked list out of it. A ternary tree is just like binary tree but instead of having two nodes, it has three nodes i.e. left, middle, right.
The doubly linked list should holds following properties –
- Left pointer of ternary tree should act as prev pointer of doubly linked list.
- Middle pointer of ternary tree should not point to anything.
- Right pointer of ternary tree should act as next pointer of doubly linked list.
- Each node of ternary tree is inserted into doubly linked list before its subtrees and for any node, its left child will be inserted first, followed by mid and right child (if any).
For the above example, the linked list formed for below tree should be NULL <- 30 <-> 5 <-> 1 <-> 4 <-> 8 <-> 11 <-> 6 <-> 7 <-> 15 <-> 63 <-> 31 <-> 55 <-> 65 -> NULL
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The idea is to traverse the tree in preoder fashion similar to binary tree preorder traversal. Here, when we visit a node, we will insert it into doubly linked list in the end using a tail pointer. That we use to maintain the required insertion order. We then recursively call for left child, middle child and right child in that order.
Below is the implementation of this idea.
Created Double Linked list is: 30 5 1 4 8 11 6 7 15 63 31 55 65
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