C# solution for Leetcode question: Find the Difference (difficulty : easy)

Source:
https://leetcode.com/problems/find-the-difference/#/description

Given two strings s and t which consist of only lowercase letters.

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

Find the letter that was added in t.

Example:

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

My C# solution is here:

https://github.com/jiajionline/LeetcodeSolutionWithMultipleLanguages/tree/master/Find%20the%20Difference