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Discover how subtracting character values in strings helps find the minimum deletions needed to make them anagrams.
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Understanding Why Character Value is Subtracted from a Given String to Find Anagrams

When working with strings in programming, you may encounter problems that require you to determine if two strings are anagrams or how many deletions are necessary to make them anagrams. In this guide, we’ll analyze a specific code snippet that utilizes character value subtraction and explore why it works effectively in solving the anagram deletion problem.

The Problem Statement

You are given two strings, s1 and s2, and your job is to find the minimum number of deletions required from s1 and s2 to make them anagrams. An anagram means that both strings can be rearranged to form the same characters with the same frequencies. The challenge arises in determining how to measure the differences in character counts efficiently.

The Code Breakdown

Let’s take a closer look at the provided code snippet and understand how character value subtraction works in achieving the solution.

[[See Video to Reveal this Text or Code Snippet]]

1. Understanding the Character Encoding

Before diving into the logic, it's important to understand how characters are represented in programming languages such as Java and C# . Each character corresponds to a numeric value based on the ASCII table. For example:

The character a corresponds to the ASCII value of 97.

The character z corresponds to the ASCII value of 122.

When you perform the operation s1[i] - 'a', you effectively convert that character into its numeric index from 0 to 25:

For a, s1[i] - 'a' becomes 97 - 97 = 0.

For b, it becomes 98 - 97 = 1, and so forth up to z.

2. Counting Character Frequencies

The core of the solution lies in using an array of size 26 (for each letter in the English alphabet). The logic in the code can be broken down as follows:

Building the Count for s1:

Each time a character from s1 is encountered, we increment its corresponding index in the array. For instance, if s1 contains 3 as, we increment array[0] by 3.

Adjusting the Count for s2:

As we check characters from s2, we decrement the counts in the same array. Thus, if s2 has 1 a, we decrement array[0] by 1. This effectively compares the frequency of each character between the two strings.

3. Calculating the Total Deletions

After processing both strings, the values in the array represent the differences in character counts between the two strings. To find the number of deletions needed, we simply compute the absolute value of each element in the array, which tells us how many characters must be removed from one or both strings to equalize their character counts.

Final Calculation:

[[See Video to Reveal this Text or Code Snippet]]

This final loop adds up all the absolute values, which gives the total number of deletions required to make the two strings anagrams.

Conclusion

In summary, the subtraction of character values in the given code allows for the efficient comparison of character frequencies across two strings. By mapping each character to an index in a fixed-size array and then performing addition and subtraction, we can readily determine how many characters need to be deleted to transform one string into an anagram of another.

Understanding this logic not only clarifies how character subtraction simplifies string manipulation but also enhances your skills in solving similar problems in the future. Happy coding!