You get leaf nodes in a tree by traversing the tree and checking each node to see if it lacks children.
In a tree data structure, a leaf node is a node that does not have any children. It marks the end point of a branch in the tree. In the context of a binary tree, a node is a leaf if both its left child and its right child are absent or NULL.
The Process to Get Leaf Nodes
According to standard methods and the provided reference, finding the leaf nodes requires visiting every node within the tree structure.
Step 1: Traverse the Tree
To identify all leaf nodes, you must traverse the tree. Tree traversal involves visiting each node in the tree exactly once. Common traversal methods include:
- In-order Traversal: Visits the left subtree, then the root node, then the right subtree.
- Pre-order Traversal: Visits the root node, then the left subtree, then the right subtree.
- Post-order Traversal: Visits the left subtree, then the right subtree, then the root node.
- Level-order Traversal: Visits nodes level by level (breadth-first).
Any of these traversal methods can be used to ensure every node is checked.
Step 2: Check Each Node for the Leaf Condition
While traversing, check every node you visit. The condition to determine if a node is a leaf is straightforward, as highlighted in the reference:
- If both the left and right child of a node is equal to NULL, it is a leaf node.
You will apply this check to every node encountered during your chosen traversal method.
Step 3: Collect Identified Leaf Nodes
As you traverse the tree and identify a node that satisfies the leaf condition (both children are NULL), you typically collect or store these nodes. This is often done by adding the node's value or a reference to the node itself into a list or an array.
Step 4: Sort the Collected Leaf Nodes
The reference mentions that after the traversal of the tree is done, we will sort the array containing the leaf nodes in ascending order. While finding the nodes is complete after Step 3, this indicates a common subsequent processing step for the collected leaf nodes. This sorting step arranges the found leaf nodes in a specific order based on their values.
In summary, the core method involves systematic traversal of the tree and a conditional check at each node based on whether its children pointers are NULL.
