Is Find the Difference easy or hard?

Find the Difference is categorized as an Easy problem. It focuses on basic string processing and simple algorithmic ideas like frequency counting or XOR cancellation, making it a common early interview practice question.

Find the Difference Python/Java solution

Python, Java, C++, C#, and JavaScript implementations typically follow either the frequency counting method or the XOR technique. Both iterate through the strings once and return the extra character detected during counting or XOR evaluation.

How to solve Find the Difference in O(n)?

Iterate through both strings and apply XOR to every character. Because identical characters cancel each other out in XOR operations, the final result will be the ASCII value of the extra character. Converting that value back to a character gives the answer in linear time.

What is the best approach for Find the Difference?

The XOR approach is typically considered the best solution. It runs in O(n) time and O(1) space while avoiding additional data structures. XOR cancels out matching characters from both strings, leaving only the extra character added to string t.

Is Find the Difference asked at Google/Amazon/Meta?

Problems involving hash tables, character counting, and XOR tricks appear frequently in interviews at companies like Amazon, Google, and Meta. While this exact problem may vary, the underlying concepts are common in string manipulation interview questions.

What data structure is used in Find the Difference?

The most common data structure is a hash table or frequency array to count character occurrences. Another efficient technique avoids data structures entirely by using bit manipulation with XOR operations.

What is the time complexity of Find the Difference?

The optimal solutions run in O(n) time, where n is the length of the strings. Both the frequency count method and the XOR approach require a single pass through the characters. Sorting-based solutions take O(n log n) due to the sorting step.

389. Find the Difference - Practice Online

You are given two strings s and t.

String t is generated by random shuffling string s and then add one more letter at a random position.

Return the letter that was added to t.

Example 1:

Input: s = "abcd", t = "abcde"
Output: "e"
Explanation: 'e' is the letter that was added.

Example 2:

Input: s = "", t = "y"
Output: "y"

Constraints:

0 <= s.length <= 1000
t.length == s.length + 1
s and t consist of lowercase English letters.