Anagram Check Techniques in DSA Java - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to convert the input strings to lowercase for case-insensitive comparison.

DSA Java

String s1Lower = s1.[1]();

Drag options to blanks, or click blank then click option'

Atrim

BtoUpperCase

CtoLowerCase

Dreplace

Attempts:

3 left

💡 Hint

Common Mistakes

Using toUpperCase instead of toLowerCase.

Forgetting to normalize case before comparison.

Using toLowerCase() converts the string to all lowercase letters, which helps in comparing anagrams without case differences.

2fill in blank

medium

Complete the code to convert the string into a character array for sorting.

DSA Java

char[] chars1 = s1Lower.[1]();

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AtoCharArray

Bsplit

CgetChars

Dsubstring

Attempts:

3 left

💡 Hint

Common Mistakes

Using split which returns a String array, not char array.

Using substring which returns a string, not an array.

toCharArray() converts the string into a char array, which can then be sorted to check for anagrams.

3fill in blank

hard

Fix the error in the sorting line to correctly sort the character array.

DSA Java

java.util.Arrays.[1](chars1);

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Asorted

Bsort

Corder

Darrange

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'sorted' which is not a method in Arrays class.

Using 'order' or 'arrange' which do not exist.

Arrays.sort() is the correct method to sort arrays in Java.

4fill in blank

hard

Fill both blanks to convert the sorted char array back to a string.

DSA Java

String sortedS1 = new String([1]); String sortedS2 = new String([2]);

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Achars1

Bchars2

Cs1Lower

Ds2Lower

Attempts:

3 left

💡 Hint

Common Mistakes

Using original strings instead of sorted char arrays.

Mixing variable names.

We create new strings from the sorted character arrays chars1 and chars2 to compare them.

5fill in blank

hard

Fill all three blanks to complete the anagram check by comparing sorted strings.

DSA Java

if ([1].equals([2])) {
    return [3];
} else {
    return false;
}

Drag options to blanks, or click blank then click option'

AsortedS1

BsortedS2

Ctrue

Dfalse

Attempts:

3 left

💡 Hint

Common Mistakes

Using '==' instead of equals() for string comparison.

Returning false when strings match.

If the sorted strings are equal, the method returns true indicating the strings are anagrams.

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