Why Anagram Check Techniques in DSA Rust?

The Big Idea

What if you could instantly tell if two words are made of the same letters without checking each letter yourself?

The Scenario

Imagine you want to check if two words are made of the same letters, like "listen" and "silent". Doing this by hand means comparing each letter one by one, which is slow and confusing.

The Problem

Manually checking each letter can take a long time and you might miss letters or count them wrong. It's easy to make mistakes, especially with longer words or many comparisons.

The Solution

Anagram check techniques use smart ways to compare words quickly, like sorting letters or counting how many times each letter appears. This makes the check fast and reliable.

Before vs After

✗ Before

fn are_anagrams_manual(word1: &str, word2: &str) -> bool {
    // Compare letters one by one manually
    // Very slow and error-prone
    false
}

✓ After

fn are_anagrams(word1: &str, word2: &str) -> bool {
    let mut chars1: Vec<char> = word1.chars().collect();
    let mut chars2: Vec<char> = word2.chars().collect();
    chars1.sort_unstable();
    chars2.sort_unstable();
    chars1 == chars2
}

What It Enables

This technique lets you quickly and correctly find if two words are anagrams, even for long words or many pairs.

Real Life Example

Spell-checkers and word games use anagram checks to find matching words or suggest corrections fast.

Key Takeaways

Manual letter-by-letter checks are slow and error-prone.

Sorting or counting letters makes anagram checks fast and reliable.

These techniques help in games, spell-checking, and text analysis.

Practice

1. What is the main idea behind checking if two strings are anagrams?

easy

A. Both strings have the same characters with the same frequency

B. Both strings have the same length only

C. Both strings start with the same character

D. Both strings contain only alphabets

Solution

1. Step 1: Understand anagram definition

   Anagrams are words or phrases made by rearranging letters of another, so character frequency must match.

2. Step 2: Compare character frequencies

   Checking if both strings have the same characters with the same counts confirms they are anagrams.

3. Final Answer:

   Both strings have the same characters with the same frequency -> Option A

4. Quick Check:

   Anagram check = same characters & frequency [OK]

Hint: Check if character counts match in both strings [OK]

Common Mistakes:

• Only comparing string lengths
• Ignoring character frequency
• Checking only first characters

2. Which Rust code snippet correctly sorts the characters of a string s to help check anagrams?

easy

A. let mut chars: Vec<char> = s.chars().collect(); chars.sort();

B. let chars = s.sort();

C. let chars = s.chars().sorted();

D. let chars = s.to_vec().sort();

Solution

1. Step 1: Collect characters into a vector

   Use s.chars().collect() to get a vector of characters from the string.

2. Step 2: Sort the vector in place

   Call chars.sort() to sort characters alphabetically for comparison.

3. Final Answer:

   let mut chars: Vec<char> = s.chars().collect(); chars.sort(); -> Option A

4. Quick Check:

   Collect chars then sort vector [OK]

Hint: Collect chars into Vec then call sort() [OK]

Common Mistakes:

• Trying to sort string directly
• Using non-existent sorted() method
• Calling sort() on &str instead of Vec<char>

3. What is the output of this Rust code snippet?

fn main() {
    let s1 = "listen";
    let s2 = "silent";
    let mut v1: Vec<char> = s1.chars().collect();
    let mut v2: Vec<char> = s2.chars().collect();
    v1.sort();
    v2.sort();
    println!("{}", v1 == v2);
}

medium

A. Runtime panic

B. true

C. Compilation error

D. false

Solution

1. Step 1: Convert strings to char vectors and sort

   Both "listen" and "silent" are converted to vectors and sorted alphabetically.

2. Step 2: Compare sorted vectors

   Sorted vectors for both strings become ['e', 'i', 'l', 'n', 's', 't'], so they are equal.

3. Final Answer:

   true -> Option B

4. Quick Check:

   Sorted chars equal means anagrams [OK]

Hint: Sort both strings and compare vectors [OK]

Common Mistakes:

• Expecting false because strings differ
• Confusing sorting with original order
• Thinking println! prints vectors directly

4. Identify the bug in this Rust function that checks if two strings are anagrams:

fn are_anagrams(s1: &str, s2: &str) -> bool {
    let mut v1: Vec<char> = s1.chars().collect();
    let mut v2: Vec<char> = s2.chars().collect();
    v1.sort();
    v2.sort();
    v1 == v2
}

fn main() {
    println!("{}", are_anagrams("abc", "cba"));
}

medium

A. Using == operator on vectors causes error

B. Missing mutable keyword for vectors

C. Should compare lengths before sorting

D. No bug, function works correctly

Solution

1. Step 1: Review vector creation and sorting

   Vectors are mutable and sorted correctly using v1.sort() and v2.sort().

2. Step 2: Check comparison and usage

   Comparing vectors with == is valid and returns true if sorted characters match.

3. Final Answer:

   No bug, function works correctly -> Option D

4. Quick Check:

   Sorting and comparing vectors works fine [OK]

Hint: Sorting vectors and comparing is valid in Rust [OK]

Common Mistakes:

• Thinking == can't compare vectors
• Assuming length check is mandatory
• Forgetting mut keyword (but it's present here)

5. You want to check if two strings are anagrams ignoring case and spaces. Which Rust approach is best?

hard

A. Sort strings without changing case or removing spaces

B. Compare strings directly after trimming spaces only

C. Convert both strings to lowercase, remove spaces, then sort and compare characters

D. Check if lengths match after removing spaces only

Solution

1. Step 1: Normalize strings by lowering case and removing spaces

   Convert both strings to lowercase and remove all spaces to ignore case and whitespace differences.

2. Step 2: Sort characters and compare

   Sort the cleaned character vectors and compare them to confirm anagram status.

3. Final Answer:

   Convert both strings to lowercase, remove spaces, then sort and compare characters -> Option C

4. Quick Check:

   Normalize case and spaces before sorting [OK]

Hint: Lowercase and remove spaces before sorting [OK]

Common Mistakes:

• Ignoring case differences
• Not removing spaces
• Comparing raw strings directly