course on Kotlin coding tests, why is debugging important?

Algorithm Problem: Two Sum

Problem Statement: Given an array of two integers and an integer target, write a program to find two numbers in the array such that their sum equals the target, and return the indices of these two numbers.

Example Input:

• nums = [2, 7, 11, 15]
• target = 9

Example Output: [0, 1]

Explanation: This is because nums[0] + nums[1] == 2 + 7 == 9.

Problem Solving Process

A basic approach to solving this problem is brute force. This involves using two nested loops to compare all possible pairs and check if they match the target. However, this method has a complexity of O(n²), so we need a more efficient algorithm.

We will traverse the given array once, storing each number’s index, and checking if the current number’s complement (target minus this number) is a previously stored value. This way, we can solve the problem with a time complexity of O(n).

Kotlin Code Example

fun twoSum(nums: IntArray, target: Int): IntArray {
    val numMap = mutableMapOf() // Map to store numbers and their indices
    for (i in nums.indices) {
        val complement = target - nums[i] // Current number's complement
        if (numMap.containsKey(complement)) { // Check if complement already exists in the map
            return intArrayOf(numMap[complement]!!, i) // Return indices
        }
        numMap[nums[i]] = i // Store current number and index
    }
    throw IllegalArgumentException("No two sum solution") // Throw exception if no solution exists
}
        

The Importance of Debugging

Thoroughly debugging the code we have while solving problems is very important. Debugging is the process of identifying and fixing bugs in the code, ensuring that it behaves as expected. Here are some debugging techniques to consider.

1. Logging

One of the most common debugging methods is to use logging. This method allows you to check the state of variables at specific points in the code. For example, you can log at the beginning and end of a function to verify the flow or log in cases where certain conditions are met to see which path the code takes.

2. Using a Debugger

By utilizing the debugging tools provided by your IDE, you can set breakpoints during code execution, monitor variable values in real-time and step through the code one line at a time. This is an effective way to identify and fix problems.

3. Unit Testing

Writing several test cases and validating them automatically through unit testing while developing algorithms is highly beneficial during the debugging process. When unexpected results occur, it becomes easy to pinpoint which case caused the issue. Defining tests in advance can improve the stability of your code.

Summary and Conclusion

Going through the process of solving algorithm problems with Kotlin requires diligent debugging. Through debugging, we can uncover hidden bugs that we may not have noticed and improve the quality of our code.

In this course, we explored the approach to solving algorithm problems and the importance of debugging through the ‘Two Sum’ problem. We hope you become familiar with Kotlin’s syntax and features and create your own algorithms through debugging.