Find the Difference

Find the Difference is a Easy Data Structures and Algorithms interview problem you can solve, run and submit on Thita.ai. It belongs to the Bit Manipulation Patterns pattern, in the Bitwise XOR - Finding Single/Missing Number subpattern.

Problem statement

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.

Topics and companies

Topics: Hash Table, String, Bit Manipulation, Sorting.

Reported in interviews at Google, Amazon.

How to practise Find the Difference on Thita.ai

Starter code is provided in C, C#, C++, Go, Java, JavaScript and Python. Your solution runs against 5 test cases for this problem, with the AI coach available for a hint when you are stuck rather than a finished answer. The reference solution runs in O(n) time and O(1) space.

Open Find the Difference in the code editor, or read the Find the Difference editorial for a worked solution with its approach and complexity analysis.

Where Find the Difference sits in the DSA pattern sheet

• Bit Manipulation Patterns pattern guide
• Bitwise XOR - Finding Single/Missing Number subpattern
• The full DSA patterns sheet
• All coding practice problems

Problems related to Find the Difference

Other problems that use the same Bitwise XOR - Finding Single/Missing Number and Bit Manipulation Patterns techniques:

• Missing Number — Easy, same subpattern
• Single Number — Easy, same subpattern
• Single Number II — Medium, same subpattern
• Counting Bits — Easy, same pattern
• Number of 1 Bits — Easy, same pattern
• Power of Four — Easy, same pattern