Anagram Check Techniques in DSA Java - 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/False based on equality

↓

Done

The flow starts by checking string lengths, then uses one of three techniques to verify if two strings are anagrams, finally returning true or false.

Execution Sample

DSA Java

String s1 = "listen";
String s2 = "silent";
boolean result = areAnagrams(s1, s2);
System.out.println(result);

Check if "listen" and "silent" are anagrams using a chosen technique and print the result.

Execution Table

Step	Operation	Data Structure State	Pointer/Index Changes	Visual State
1	Input strings s1="listen", s2="silent"	s1: "listen", s2: "silent"	N/A	s1: listen s2: silent
2	Check length equality	length(s1)=6, length(s2)=6	N/A	Lengths equal, proceed
3	Sort s1 and s2	s1 sorted: "eilnst", s2 sorted: "eilnst"	N/A	s1 sorted: eilnst s2 sorted: eilnst
4	Compare sorted strings	Comparing each char	Index from 0 to 5	All characters match
5	Return result	true	N/A	Result: true
6	Print result	Output: true	N/A	Printed: true

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

Variable Tracker

Variable	Start	After Step 3	After Step 4	Final
s1	"listen"	"eilnst"	"eilnst"	"eilnst"
s2	"silent"	"eilnst"	"eilnst"	"eilnst"
result	undefined	undefined	true	true

Key Moments - 3 Insights

Why do we check string lengths first before other operations?

If lengths differ (see Step 2 in execution_table), strings cannot be anagrams, so we stop early to save time.

Why do we sort both strings before comparing?

Sorting arranges characters in order, so if sorted strings match (Step 4), original strings are anagrams.

Can we use character counts instead of sorting?

Yes, counting characters and comparing counts is another technique (not shown here) that avoids sorting but achieves the same result.

Visual Quiz - 3 Questions

Look at the execution_table at Step 3, what is the sorted form of s1?

A "listen"

B "eilnst"

C "silent"

D "enlist"

💡 Hint

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

At which step does the program decide the strings are anagrams?

A Step 2

B Step 4

C Step 5

D Step 6

💡 Hint

Look for the step where the result variable is set to true in variable_tracker and execution_table.

If s1 was "listen" and s2 was "silents", what would happen at Step 2?

A Proceed to sorting

B Return false immediately

C Compare sorted strings

D Throw an error

💡 Hint

Step 2 checks if lengths are equal before any other operation.

Concept Snapshot

Anagram Check Techniques:
- Step 1: Check if strings have equal length.
- Step 2: Use sorting or character counting.
- Sorting: sort both strings and compare.
- Counting: count chars and compare counts.
- Return true if equal, else false.

Full Transcript

This visual execution trace shows how to check if two strings are anagrams. First, the program inputs two strings and checks if their lengths are equal. If not, it returns false immediately. If lengths match, it sorts both strings and compares them character by character. If all characters match, it returns true, indicating the strings are anagrams. The trace tracks variables and shows the state of strings after sorting. Key moments clarify why length check is important and why sorting helps. The quiz tests understanding of sorted forms, decision steps, and length checks.

Practice

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

easy

A. They end with the same character

B. They have the same length but different characters

C. They start with the same character

D. They contain the same characters in any order

Solution

1. Step 1: Understand the definition of anagrams

   Anagrams are words or phrases made by rearranging the letters of another, using all original letters exactly once.

2. Step 2: Compare character sets

   If two strings have the same characters with the same frequency, they are anagrams regardless of order.

3. Final Answer:

   They contain the same characters in any order -> Option D

4. Quick Check:

   Anagrams = same characters any order [OK]

Hint: Check if sorted strings match to confirm anagrams [OK]

Common Mistakes:

• Thinking same length means anagrams
• Only comparing first or last characters
• Ignoring character frequency

2. Which Java code snippet correctly checks if two strings s1 and s2 are anagrams using sorting?

easy

A. char[] a1 = s1.toCharArray(); char[] a2 = s2.toCharArray(); Arrays.sort(a1); Arrays.sort(a2); return Arrays.equals(a1, a2);

B. Arrays.sort(s1.toCharArray()); Arrays.sort(s2.toCharArray()); return s1.equals(s2);

C. return s1.equalsIgnoreCase(s2);

D. return s1.length() == s2.length();

Solution

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

   We must convert strings to char arrays because Arrays.sort works on arrays, not strings.

2. Step 2: Compare sorted arrays for equality

   After sorting, if arrays are equal, strings are anagrams. Use Arrays.equals to compare arrays.

3. Final Answer:

   char[] a1 = s1.toCharArray(); char[] a2 = s2.toCharArray(); Arrays.sort(a1); Arrays.sort(a2); return Arrays.equals(a1, a2); -> Option A

4. Quick Check:

   Sort char arrays and compare arrays [OK]

Hint: Sort char arrays, then compare with Arrays.equals [OK]

Common Mistakes:

• Sorting strings directly without converting to char arrays
• Using equals() on unsorted strings
• Comparing only lengths

3. What will be the output of the following Java code?

String s1 = "listen";
String s2 = "silent";
char[] a1 = s1.toCharArray();
char[] a2 = s2.toCharArray();
Arrays.sort(a1);
Arrays.sort(a2);
System.out.println(Arrays.equals(a1, a2));

medium

A. Runtime exception

B. false

C. true

D. Compilation error

Solution

1. Step 1: Convert and sort both strings

   Both strings "listen" and "silent" are converted to char arrays and sorted. Sorted arrays become ['e','i','l','n','s','t'] for both.

2. Step 2: Compare sorted arrays

   Since sorted arrays are identical, Arrays.equals(a1, a2) returns true.

3. Final Answer:

   true -> Option C

4. Quick Check:

   Sorted arrays match = true [OK]

Hint: Sort and compare arrays to check anagrams [OK]

Common Mistakes:

• Assuming order matters without sorting
• Confusing equals() on strings with arrays
• Forgetting to sort arrays

4. Identify the error in this Java method that checks if two strings are anagrams:

public boolean isAnagram(String s1, String s2) {
  if (s1.length() != s2.length()) return false;
  char[] a1 = s1.toCharArray();
  char[] a2 = s2.toCharArray();
  Arrays.sort(a1);
  Arrays.sort(a2);
  return a1.equals(a2);
}

medium

A. Using a1.equals(a2) compares references, not content

B. Missing length check before sorting

C. Sorting arrays is incorrect for anagram check

D. Method should return void, not boolean

Solution

1. Step 1: Understand array equality in Java

   Using a1.equals(a2) compares if both arrays are the same object, not their contents.

2. Step 2: Use correct method to compare arrays

   To compare contents, use Arrays.equals(a1, a2) instead of a1.equals(a2).

3. Final Answer:

   Using a1.equals(a2) compares references, not content -> Option A

4. Quick Check:

   Use Arrays.equals() for array content comparison [OK]

Hint: Use Arrays.equals() to compare array contents [OK]

Common Mistakes:

• Using equals() on arrays instead of Arrays.equals()
• Ignoring length check
• Returning wrong data type

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

hard

A. Compare strings directly with equalsIgnoreCase()

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

C. Count characters without removing spaces or changing case

D. Check if lengths are equal and first characters match

Solution

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

   Removing spaces and converting to lowercase ensures uniform comparison ignoring case and spaces.

2. Step 2: Sort char arrays and compare

   After normalization, convert to char arrays, sort them, and compare to check anagram status.

3. Final Answer:

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

4. Quick Check:

   Normalize then sort and compare [OK]

Hint: Normalize strings before sorting to ignore case and spaces [OK]

Common Mistakes:

• Not removing spaces before comparison
• Ignoring case differences
• Only comparing lengths or first characters