Hello! In this article, we will take a detailed look at the algorithm problem of finding the parent of a tree using JavaScript. We will emphasize the importance of understanding tree structures and their application in coding tests, and we will systematically organize how to solve related problems step by step. In particular, we will discuss what it means to understand the definition of a tree and the parent-finding algorithm in coding tests.
What is a Tree Structure?
A tree is one of the data structures that has a hierarchical structure. It is a type of graph made up of nodes and the connections between those nodes. A tree has the following characteristics:
- A tree is a non-linear structure.
- A tree consists of one or more child nodes (Child Node) and a root node (Root Node).
- Each node can have one parent node (Parent Node), and the root node has no parent.
- A tree does not contain cycles.
Problem Description
In this problem, we need to implement an algorithm to find the parent node of a specific node in a given tree structure. It has the following input format:
Example input:
{
"1": [2, 3],
"2": [4, 5],
"3": [],
"4": [],
"5": []
}
In the example above, each key represents a node, and the value is an array of child nodes of that node. For example, node 1 has 2 and 3 as children.
Requirements
- Create a function to find the parent node of a specific node.
- It should be able to parse the tree structure through the input format.
- If there is no parent node, it should return null.
Problem Solving Process
Now, let’s look step-by-step at how to parse the tree structure and find the parent node to solve the problem.
Step 1: Parsing the Tree Structure
First, we need to parse the tree structure based on the given input. The example tree we will deal with is transmitted in object form, and we need a structure that can store parent information based on child nodes and their relationships in order to find the parents.
const tree = {
"1": [2, 3],
"2": [4, 5],
"3": [],
"4": [],
"5": []
};
Each node of the tree can be accessed in adjacency list form. However, to find parent information, we must explicitly store the parents of each node. To do this, we will create a new object and update the parent information while traversing the child nodes.
Step 2: Implementing the Parent Finding Logic
Finding a parent involves checking which parent each node has in the tree structure. The function can be implemented in the following steps:
const findParent = (tree, child) => {
let parentNode = null;
for (const key in tree) {
if (tree[key].includes(child)) {
parentNode = key;
break;
}
}
return parentNode ? parentNode : null;
};
The above `findParent` function accepts the tree object and the child node as input and searches for the parent node of that child. It checks each node for the child node and returns the parent node found in the node that includes the child. If there is no parent, it returns null.
Step 3: Implementing the Full Code
Now, let’s integrate the parts we have written above to complete the full code.
const tree = {
"1": [2, 3],
"2": [4, 5],
"3": [],
"4": [],
"5": []
};
const findParent = (tree, child) => {
let parentNode = null;
for (const key in tree) {
if (tree[key].includes(child)) {
parentNode = key;
break;
}
}
return parentNode ? parentNode : null;
};
// Example usage
console.log(findParent(tree, 4)); // Output: "2"
console.log(findParent(tree, 5)); // Output: "2"
console.log(findParent(tree, 1)); // Output: null
Conclusion
In this lecture, we explored the process of solving the algorithm problem of finding the parent of a child node in a tree structure using JavaScript. Understanding tree structures and solving algorithm problems using them is an important skill for developers. As we become more familiar with various tree structures, we can effectively solve many problems through tree traversal techniques.
In the future, we will cover a wider range of algorithms and data structures. Thank you!