Kotlin Language Features Related to Null Handling

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Any software engineer with a Java background would find the null handling features in the Kotlin language interesting. Let's summarize this topic with some examples. Nullable types: In Kotlin, types are non-nullable by default. If you want a variable to be able to hold a null value, you need to explicitly declare its type as nullable using the Type? syntax. For example, String? denotes a nullable string, while String represents a non-nullable string. Safe calls (?.): Kotlin introduces the safe call operator (?.) for handling nullable types. It allows you to safely invoke a method or access a property on a nullable object. If the object is null, the expression returns null instead of throwing a NullPointerException. Example: data class Person(val name: String, val age: Int, val address: String?) fun main() {     // Create a person with a nullable address     val person1 = Person("John Doe", 25, "123 Main Street")     val person2 = Person("Jane Doe", 30,...
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My Crappy Looking Solution to "Binary Tree Common Ancestor" Problem

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I was able to solve this problem and make all the tests pass:

https://www.hackerrank.com/challenges/binary-search-tree-lowest-common-ancestor/problem

But I'm not happy with the code, so later I need to refactor the code. Here it is:

static Node lca(Node root, int v1, int v2) {

    ArrayList result = new ArrayList<>();

    Node result2 =
            traverse(root, v1, v2, result);

    if (result.isEmpty())
        return result2;

    return result.get(0);
}


private static Node traverse(Node root, int v1, int v2, ArrayList result) {

    if (!result.isEmpty()) {
        return result.get(0);
    }

    if (root.left == null && root.right == null) {
        return root;
    }

    if (root.data == v1 || root.data == v2) {
        return root;
    }

    Node node1 = null, node2 = null;

    if (root.left != null)
        node1 = traverse(root.left, v1, v2, result);

    if (root.right != null)
        node2 = traverse(root.right, v1, v2, result);

    if (!result.isEmpty()) {
        return result.get(0);
    }

    if (node1 != null && node1.data == v1 &&
            node2 != null && node2.data == v2) {
        result.add(root);
        return root;
    }
    if (node1 != null && node1.data == v2 &&
            node2 != null && node2.data == v1) {
        result.add(root);
        return root;
    }


    if (node1 == null && node2 == null)
        return null;

    if (node1 != null && node1.data == v1) {
        return node1;
    }
    if (node1 != null && node1.data == v2) {
        return node1;
    }
    if (node2 != null && node2.data == v1) {
        return node2;
    }
    if (node2 != null && node2.data == v2) {
        return node2;
    }


    return null;
}




Thanks to this youtube channel for describing the algorithm:




https://www.youtube.com/watch?v=F-_1sbnPbWQ&t=301s


































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