Anagram Check Techniques in DSA C# - Execution Trace

Concept Flow - Anagram Check Techniques

Input two strings

↓

Check length equal?

No→Return False

Yes↓

Choose technique

↓

Sort & Compare

↓

Compare sorted

↓

Return True if equal, else False

The flow starts by checking if two strings have the same length. If yes, it proceeds with one of the anagram check methods: sorting, counting characters, or using dictionaries, then compares results to decide.

Execution Sample

DSA C#

string s1 = "listen";
string s2 = "silent";
bool result = AreAnagrams(s1, s2);
Console.WriteLine(result);

This code checks if 'listen' and 'silent' are anagrams using a chosen technique and prints True or False.

Execution Table

Step	Operation	Data Structure State	Pointer/Index Changes	Visual State
1	Input strings s1='listen', s2='silent'	s1: 'listen', s2: 'silent'	None	s1: l -> i -> s -> t -> e -> n s2: s -> i -> l -> e -> n -> t
2	Check length equal	Length s1=6, Length s2=6	None	Lengths equal, proceed
3	Sort s1 and s2	s1 sorted: ['e','i','l','n','s','t'], s2 sorted: ['e','i','l','n','s','t']	Indices 0 to 5 sorted	s1 sorted: e -> i -> l -> n -> s -> t s2 sorted: e -> i -> l -> n -> s -> t
4	Compare sorted arrays	Comparing each index	Index 0 to 5	All characters match at each position
5	Return True	Result = True	None	Anagram confirmed

💡 All characters matched after sorting, so strings are anagrams.

Variable Tracker

Variable	Start	After Step 3	After Step 4	Final
s1	"listen"	[ 'e','i','l','n','s','t' ]	[ 'e','i','l','n','s','t' ]	"listen" (original unchanged)
s2	"silent"	[ 'e','i','l','n','s','t' ]	[ 'e','i','l','n','s','t' ]	"silent" (original unchanged)
result	undefined	undefined	undefined	True

Key Moments - 3 Insights

Why do we check string lengths first before other operations?

Because if lengths differ, they cannot be anagrams. This quick check (Step 2) saves unnecessary work like sorting or counting.

Why do we sort both strings before comparing?

Sorting arranges characters in order, so if both sorted arrays match exactly (Step 4), the strings are anagrams.

Can we modify the original strings during sorting?

No, original strings remain unchanged. Sorting creates new arrays or copies (Step 3), preserving original data.

Visual Quiz - 3 Questions

Look at the execution table, what is the sorted state of s1 after Step 3?

A ['s','i','l','e','n','t']

B ['l','i','s','t','e','n']

C ['e','i','l','n','s','t']

D ['t','s','n','l','i','e']

💡 Hint

Check the 'Data Structure State' column in Step 3.

At which step do we confirm that the strings are anagrams?

A Step 5

B Step 2

C Step 4

D Step 3

💡 Hint

Look for the step where the result is returned as True.

If the strings had different lengths, what would happen according to the flow?

A Proceed to sorting

B Return False immediately

C Count characters anyway

D Compare dictionaries

💡 Hint

Refer to the decision after 'Check length equal?' in the concept flow.

Concept Snapshot

Anagram Check Techniques:
- First, check if strings have equal length.
- Then use one method: sort & compare, count chars, or dictionary.
- Sorting method: sort both strings and compare character by character.
- If all characters match, strings are anagrams.
- Return True if anagrams, else False.

Full Transcript

This visualization shows how to check if two strings are anagrams. We start by inputting two strings and checking if their lengths are equal. If not, we return False immediately. If lengths match, we proceed with a technique such as sorting both strings and comparing them character by character. The execution table traces each step: input, length check, sorting, comparison, and final result. Variables like the original strings and sorted arrays are tracked to show their states. Key moments clarify why length check is important, why sorting helps, and that original strings remain unchanged. The quiz tests understanding of sorted states, confirmation step, and early exit on length mismatch. The snapshot summarizes the process simply for quick recall.

Practice

1. What does it mean if two strings are anagrams of each other?

easy

A. They have the same characters in the same frequency but possibly different order

B. They have the same length but different characters

C. They start with the same letter

D. They contain only vowels

Solution

1. Step 1: Understand the definition of anagrams

   Anagrams are words or phrases made by rearranging the letters of another, so they must have the same characters with the same counts.

2. Step 2: Compare the options

   Only They have the same characters in the same frequency but possibly different order correctly describes this property; others describe unrelated conditions.

3. Final Answer:

   They have the same characters in the same frequency but possibly different order -> Option A

4. Quick Check:

   Anagram = Same chars & frequency [OK]

Hint: Anagrams have same letters and counts, order doesn't matter [OK]

Common Mistakes:

• Thinking same length means anagram
• Assuming order must be identical
• Confusing anagrams with substrings

2. Which of the following C# code snippets correctly checks if two strings are anagrams by sorting?

easy

A. return s1.Contains(s2);

B. return s1 == s2;

C. return s1.Length == s2.Length;

D. return string.Concat(s1.OrderBy(c => c)) == string.Concat(s2.OrderBy(c => c));

Solution

1. Step 1: Understand sorting approach for anagrams

   Sorting both strings and comparing them checks if they have the same characters in the same order after sorting.

2. Step 2: Analyze each code snippet

   return string.Concat(s1.OrderBy(c => c)) == string.Concat(s2.OrderBy(c => c)); sorts both strings and compares; this is correct. Options B, C, and D do not check anagram conditions properly.

3. Final Answer:

   return string.Concat(s1.OrderBy(c => c)) == string.Concat(s2.OrderBy(c => c)); -> Option D

4. Quick Check:

   Sort & compare strings = correct anagram check [OK]

Hint: Sort both strings and compare to check anagrams [OK]

Common Mistakes:

• Comparing strings directly without sorting
• Only checking length equality
• Using Contains instead of full comparison

3. What will be the output of the following C# code?

string s1 = "listen";
string s2 = "silent";
bool result = s1.OrderBy(c => c).SequenceEqual(s2.OrderBy(c => c));
Console.WriteLine(result);

medium

A. True

B. False

C. Compilation error

D. Runtime exception

Solution

1. Step 1: Sort both strings and compare sequences

   The code sorts characters of both strings and checks if sequences are equal. "listen" and "silent" are anagrams.

2. Step 2: Evaluate the result of SequenceEqual

   Since sorted characters match, SequenceEqual returns true, so Console.WriteLine prints True.

3. Final Answer:

   True -> Option A

4. Quick Check:

   Sorted anagrams equal = True [OK]

Hint: Sorted anagrams produce true when compared with SequenceEqual [OK]

Common Mistakes:

• Assuming order matters before sorting
• Confusing SequenceEqual with Equals
• Expecting false because strings differ initially

4. Identify the bug in this C# method intended to check anagrams:

bool AreAnagrams(string s1, string s2) {
  if (s1.Length != s2.Length) return false;
  var dict = new Dictionary();
  foreach (var c in s1) {
    dict[c] = dict.ContainsKey(c) ? dict[c] + 1 : 1;
  }
  foreach (var c in s2) {
    if (!dict.ContainsKey(c)) return false;
    dict[c]--;
  }
  return true;
}

medium

A. It does not check string lengths

B. It uses a dictionary instead of array

C. It does not check if counts go below zero

D. It returns false too early

Solution

1. Step 1: Review dictionary count decrement logic

   The method decrements counts for characters in s2 but never checks if count becomes negative, which means extra characters in s2 are not detected.

2. Step 2: Identify missing validation

   Without checking if dict[c] < 0 after decrement, method can wrongly return true when s2 has extra characters.

3. Final Answer:

   It does not check if counts go below zero -> Option C

4. Quick Check:

   Check negative counts after decrement to fix bug [OK]

Hint: Always verify counts don't go negative when decrementing [OK]

Common Mistakes:

• Ignoring negative counts after decrement
• Assuming length check is enough
• Not using dictionary for frequency

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

hard

A. Count characters without removing spaces

B. Remove spaces, convert to lowercase, then sort and compare

C. Compare strings directly ignoring case

D. Check if lengths are equal ignoring spaces

Solution

1. Step 1: Normalize strings by removing spaces and converting to lowercase

   This ensures spaces and case differences do not affect comparison.

2. Step 2: Sort normalized strings and compare

   Sorting both normalized strings and comparing confirms if they are anagrams ignoring case and spaces.

3. Final Answer:

   Remove spaces, convert to lowercase, then sort and compare -> Option B

4. Quick Check:

   Normalize then sort & compare for case/space insensitive anagram [OK]

Hint: Normalize strings by removing spaces and lowercasing before checking [OK]

Common Mistakes:

• Not removing spaces before comparison
• Ignoring case differences
• Only checking length equality