## Sunday, May 8, 2016

### Non-recursive program to delete an entire binary tree. - GeeksforGeeks

Non-recursive program to delete an entire binary tree. - GeeksforGeeks
Now how to delete an entire tree without using recursion. This could easily be done with the help of Level Order Tree Traversal. The idea is for each dequeued node from the queue, delete it after queuing its left and right nodes (if any). The solution will work as we are traverse all the nodes of the tree level by level from top to bottom, and before deleting the parent node, we are storing its children into queue that will be deleted later.

`void` `_deleteTree(Node *root)`
`{`
`    ``// Base Case`
`    ``if` `(root == NULL)`
`        ``return``;`

`    ``// Create an empty queue for level order traversal`
`    ``queue<Node *> q;`

`    ``// Do level order traversal starting from root`
`    ``q.push(root);`
`    ``while` `(!q.empty())`
`    ``{`
`        ``Node *node = q.front();`
`        ``q.pop();`

`        ``if` `(node->left != NULL)`
`            ``q.push(node->left);`
`        ``if` `(node->right != NULL)`
`            ``q.push(node->right);`

`        ``free``(node);`
`    ``}`
`}`

`def` `_deleteTree(root):`
`    `
`    ``# Base Case`
`    ``if` `root ``is` `None``:`
`        ``return`

`    ``# Create a empty queue for level order traversal`
`    ``q ``=` `[]`

`    ``# Do level order traversal starting from root`
`    ``q.append(root)`
`    ``while``(``len``(q)>``0``):`
`        ``node ``=` `q.pop(``0``)`
`    `
`        ``if` `node.left ``is` `not` `None``:`
`            ``q.append(node.left)`

`        ``if` `node.right ``is` `not` `None``:`
`            ``q.append(node.right)`

`        ``node ``=` `None`
`    ``return` `node`

`# Deletes a tree and sets the root as None`
`def` `deleteTree(node_ref):`
`    ``node_ref ``=` `_deleteTree(node_ref)`
`    ``return` `node_ref`