kotlin coding test course, examining debugging use cases

In modern programming environments, coding tests are becoming an essential element.
Especially, they are establishing themselves as one of the various methods to find outstanding talents in the software development field.
This article will explore the algorithm problem-solving process using the Kotlin language,
along with how to effectively solve problems using debugging.

Algorithm Problem: Two Sum

Given an integer array nums and an integer target,
the problem is to select two numbers from nums such that their sum returns the indices that equal target.
You cannot use the same element twice, and it is assumed that there is exactly one solution.
The problem can be summarized as follows.

Problem Description

  • Input: nums = [2, 7, 11, 15], target = 9
  • Output: [0, 1] (nums[0] + nums[1] = 2 + 7 = 9)

How to Solve the Problem

There can be several methods to solve this problem, but one of the most efficient ways is to use a hash map.
Using a hash map allows us to find elements with an average time complexity of O(1).

Algorithm Approach

  • Initialize a hash map.
  • Iterate through the array and calculate the differences for each element.
  • Check if this difference already exists in the hash map.
  • If it exists, return the corresponding index; otherwise, store the current element and its index in the hash map.

Code Implementation

        
fun twoSum(nums: IntArray, target: Int): IntArray {
    val map = mutableMapOf()

    for ((index, num) in nums.withIndex()) {
        val complement = target - num
        if (map.containsKey(complement)) {
            return intArrayOf(map[complement]!!, index)
        }
        map[num] = index
    }
    throw IllegalArgumentException("No two sum solution")
}

Using Debugging

The code above implements the basic logic; however, in an actual coding test, various errors that may occur during execution need to be considered.
Here, we will explain how to use debugging tools.

Kotlin Debugging Methods

  • Utilizing the IDE’s Debugging Features: In IDEs like IntelliJ IDEA, you can step through the code execution step by step to find out where issues occur.
  • Log Output: You can use log outputs, such as println, to print the value of specific variables or track the progress of the code. For example, you might print the contents of the hash map to find overlapping values.
  • Exception Handling: In case of exceptions, you can determine where the issue occurred by using appropriate error messages.
    For instance, if the problem’s data differs from what is expected, an IllegalArgumentException-related error message can be printed.

Problem Solving Through Debugging Process

  1. First, write the code, set a few input values, and run it in debugging mode.
  2. Check the value of variables at each step and compare them against expected results.
  3. Inspect the state values or changes in the hash map to ensure that the correct index is being tracked.
  4. If it does not function correctly, change the conditions to find the root cause and add logs to test various scenarios.
  5. Once the issue is resolved, review the final code and check for any areas that can be optimized.

Conclusion

Solving algorithm problems using Kotlin begins with choosing efficient data structures and algorithms.
Debugging techniques are crucial skills for developers, allowing them to resolve issues through appropriate approaches when problems arise.
Additionally, through practice with various problems, debugging skills can also be developed.

If you are preparing for a coding test, it is important to not only understand the problem but also to gain experience in tracking and solving the root causes of issues using debugging.
I hope you enjoy and efficiently prepare for coding tests by utilizing the various features provided by the Kotlin language!