Missing Test Case - 1768. Merge Strings Alternately

Problem Description

The problem "Merge Strings Alternately" is a simple yet interesting question on the LeetCode platform. It requires the test cases to be merged alternately, which can be achieved using a StringBuilder in Java. However, there seems to be a missing test case in the problem, which we will discuss in this article.

Problem Statement

Given two strings s1 and s2, merge them alternately of non-empty strings. If one of the strings is longer than the other, in the result all the characters in the longer string should be used, and the remaining empty string's place should be filled with a space.

Example 1: Input: s1 = "abc", s2 = "pqr" Output: "apbqcr"

Example 2: Input: s1 = "ab", s2 = "pqrs" Output: "apbqrs"

Example 3: Input: s1 = "abcd", s2 = "" Output: "a b c d"

Example 4: Input: s1 = "", s2 = "pqrs" Output: "p q r s"

Example 5: Input: s1 = "ab", s2 = "pq" Output: "apbq"

Code Solution

Here is a simple Java code solution using a StringBuilder to merge the strings alternately:

public class Solution {
    public String mergeAlternately(String word1, String word2) {
        StringBuilder sb = new StringBuilder();
        int len1 = word1.length();
        int len2 = word2.length();
        int minLen = Math.min(len1, len2);
        
        for (int i = 0; i < minLen; i++) {
            sb.append(word1.charAt(i));
            sb.append(word2.charAt(i));
        }
        
        if (len1 > len2) {
            for (int i = minLen; i < len1; i++) {
                sb.append(word1.charAt(i));
            }
        } else if (len2 > len1) {
            for (int i = minLen; i < len2; i++) {
                sb.append(word2.charAt(i));
            }
        }
        
        return sb.toString();
    }
}

Missing Test Case

The problem statement seems to be missing a test case where one of the strings is empty and the other string is not empty. In this case, the output should be the non-empty string with a space in between each character.

Example 6: Input: s1 = "", s2 = "pqrs" Output: "p q r s"

However, the problem statement does not mention this test case, which makes it incomplete.

Conclusion

In conclusion, the problem "Merge Strings Alternately" is a simple yet interesting question on the LeetCode platform. However, there seems to be a missing test case in the problem, which makes it incomplete. The code solution using a StringBuilder is a simple and efficient way to merge the strings alternately.

Recommendation

To make the problem complete, the test case where one of the strings empty and the other string is not empty should be added. This will make the problem more comprehensive and challenging for the test-takers.

Future Work

In the future, the problem can be modified to include more test cases, such as:

• Test case where both strings are empty
• Test case where both strings are not empty but have different lengths
• Test case where one of the strings is a palindrome and the other string is not a palindrome

By including these test cases, the problem will become more comprehensive and challenging for the test-takers.

References

• LeetCode: Merge Strings Alternately (https://leetcode.com/problems/merge-strings-alternately/?envType=study-plan-v2&envId=programming-skills)
• Java StringBuilder (https://docs.oracle.com/javase/8/docs/api/java/lang/StringBuilder.html)
  Q&A: Missing Test Case - 1768. Merge Strings Alternately =====================================================

Q: What is the problem "Merge Strings Alternately" on LeetCode?

A: The problem "Merge Strings Alternately" is a simple yet interesting question on the LeetCode platform. It requires the test cases to be merged alternately, which can be achieved using a StringBuilder in Java.

Q: What is the problem statement of "Merge Strings Alternately"?

A: The problem statement is as follows:

Given two strings s1 and s2, merge them alternately of non-empty strings. If one of the strings is longer than the other, in the result all the characters in the longer string should be used, and the remaining empty string's place should be filled with a space.

Q: What are the example test cases for "Merge Strings Alternately"?

A: The example test cases are as follows:

• Example 1: Input: s1 = "abc", s2 = "pqr" Output: "apbqcr"
• Example 2: Input: s1 = "ab", s2 = "pqrs" Output: "apbqrs"
• Example 3: Input: s1 = "abcd", s2 = "" Output: "a b c d"
• Example 4: Input: s1 = "", s2 = "pqrs" Output: "p q r s"
• Example 5: Input: s1 = "ab", s2 = "pq" Output: "apbq"

Q: What is the missing test case in "Merge Strings Alternately"?

A: The missing test case is where one of the strings is empty and the other string is not empty. In this case, the output should be the non-empty string with a space in between each character.

Q: How can the missing test case be added to the problem?

A: The missing test case can be added by including the following test case:

• Example 6: Input: s1 = "", s2 = "pqrs" Output: "p q r s"

Q: What is the code solution for "Merge Strings Alternately"?

A: The code solution using a StringBuilder is as follows:

public class Solution {
    public String mergeAlternately(String word1, String word2) {
        StringBuilder sb = new StringBuilder();
        int len1 = word1.length();
        int len2 = word2.length();
        int minLen = Math.min(len1, len2);
        
        for (int i = 0; i < minLen; i++) {
            sb.append(word1.charAt(i));
            sb.append(word2.charAt(i));
        }
        
        if (len1 > len2) {
            for (int i = minLen; i < len1; i++) {
                sb.append(word1.charAt(i));
            }
        } else if (len2 > len1) {
            for (int i = minLen; i < len2; i++) {
                sb.append(word2.charAt(i));
            }
        }
        
        return sb.toString();
    }
}

Q: are the benefits of including the missing test case?

A: The benefits of including the missing test case are:

• The problem becomes more comprehensive and challenging for the test-takers.
• The test-takers can learn more about the problem and improve their skills.
• The problem becomes more realistic and reflects real-world scenarios.

Q: What are the future work recommendations for "Merge Strings Alternately"?

A: The future work recommendations are:

• Include more test cases, such as:
  • Test case where both strings are empty
  • Test case where both strings are not empty but have different lengths
  • Test case where one of the strings is a palindrome and the other string is not a palindrome
• Modify the problem to include more challenging scenarios, such as:
  • Strings with special characters
  • Strings with different lengths
  • Strings with different formats

By including these test cases and modifying the problem, the test-takers can learn more about the problem and improve their skills.