Get Full Names II in Java - Time Complexity: O(n)

Given an array of strings names that contain first and last names adjacent to each other, return an array containing the full names (separated by one space)

Example:

Input:  names = ["John", "Doe", "Andy", "Smith", "Mary", "Johnson"]

Output:  ["John Doe", "Andy Smith", "Mary Johnson"]

Understanding the Problem

The core challenge of this problem is to pair adjacent elements in the input array to form full names. Each pair of elements represents a first name followed by a last name. The significance of this problem lies in its simplicity and its application in data processing tasks where names are often split and need to be combined.

Potential pitfalls include assuming that the input array will always have an even number of elements or that the names will always be properly paired. Misconceptions might arise if one assumes that the names are separated by more than one space or that additional processing is required.

Approach

To solve this problem, we can iterate through the input array in steps of two, combining each pair of elements into a single string. This approach ensures that we efficiently process the array in linear time.

A naive solution might involve iterating through the array and manually managing indices, but this can be error-prone and less readable. Instead, we can use a loop that increments by two to directly access each pair of elements.

Algorithm

1. Initialize an empty list to store the full names.
2. Iterate through the input array in steps of two.
3. For each pair of elements, concatenate them with a space in between and add the result to the list.
4. Return the list of full names.

Code Implementation

import java.util.ArrayList;
import java.util.List;

public class FullNames {
    public static List<String> getFullNames(String[] names) {
        // Initialize a list to store the full names
        List<String> fullNames = new ArrayList<>();
        
        // Iterate through the array in steps of two
        for (int i = 0; i < names.length; i += 2) {
            // Combine the first name and last name with a space
            String fullName = names[i] + " " + names[i + 1];
            // Add the full name to the list
            fullNames.add(fullName);
        }
        
        // Return the list of full names
        return fullNames;
    }

    public static void main(String[] args) {
        // Example usage
        String[] names = {"John", "Doe", "Andy", "Smith", "Mary", "Johnson"};
        List<String> result = getFullNames(names);
        System.out.println(result); // Output: [John Doe, Andy Smith, Mary Johnson]
    }
}

Complexity Analysis

The time complexity of this approach is O(n), where n is the number of elements in the input array. This is because we iterate through the array once, processing each pair of elements. The space complexity is O(n/2) = O(n), as we store half the number of elements in the output list.

Edge Cases

Potential edge cases include:

• An empty input array, which should return an empty list.
• An input array with an odd number of elements, which is invalid based on the problem constraints.

To handle these cases, we can add checks to ensure the input array has an even number of elements and is not empty.

Testing

To test the solution comprehensively, we should include a variety of test cases:

• Simple cases with a few names.
• Edge cases with an empty array.
• Cases with a large number of names to test performance.

We can use JUnit or another testing framework to automate these tests.

Thinking and Problem-Solving Tips

When approaching such problems, it's important to:

• Understand the input and output formats clearly.
• Break down the problem into smaller, manageable steps.
• Consider edge cases and constraints early in the process.
• Write clean, readable code with comments to explain your thought process.

Practicing similar problems and studying algorithms can help improve problem-solving skills.

Conclusion

In this blog post, we discussed how to solve the problem of combining adjacent first and last names into full names. We explored the problem definition, approach, algorithm, code implementation, complexity analysis, edge cases, and testing. Understanding and solving such problems is crucial for data processing tasks and helps improve coding skills.

Additional Resources

For further reading and practice, consider the following resources:

• LeetCode - Practice coding problems and challenges.
• GeeksforGeeks - Tutorials and explanations of various algorithms and data structures.
• Coursera - Online courses on algorithms and data structures.