389. Find the Difference

Problem Description

You are given two strings s and t.

String t is generated by random shuffling string s and then adding 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.

Python Solution

class Solution:
    def findTheDifference(self, s: str, t: str) -> str:
        # XOR approach
        result = 0
        
        # XOR all characters in s
        for char in s:
            result ^= ord(char)
            
        # XOR all characters in t
        for char in t:
            result ^= ord(char)
            
        # The remaining value is the added character
        return chr(result)

Java Solution

class Solution {
    public char findTheDifference(String s, String t) {
        // XOR approach
        int result = 0;
        
        // XOR all characters in s
        for (char c : s.toCharArray()) {
            result ^= c;
        }
        
        // XOR all characters in t
        for (char c : t.toCharArray()) {
            result ^= c;
        }
        
        // The remaining value is the added character
        return (char) result;
    }
}

C++ Solution

class Solution {
public:
    char findTheDifference(string s, string t) {
        // XOR approach
        char result = 0;
        
        // XOR all characters in s
        for (char c : s) {
            result ^= c;
        }
        
        // XOR all characters in t
        for (char c : t) {
            result ^= c;
        }
        
        // The remaining value is the added character
        return result;
    }
};

JavaScript Solution

/**
 * @param {string} s
 * @param {string} t
 * @return {character}
 */
var findTheDifference = function(s, t) {
    // XOR approach
    let result = 0;
    
    // XOR all characters in s
    for (let char of s) {
        result ^= char.charCodeAt(0);
    }
    
    // XOR all characters in t
    for (let char of t) {
        result ^= char.charCodeAt(0);
    }
    
    // The remaining value is the added character
    return String.fromCharCode(result);
};

C# Solution

public class Solution {
    public char FindTheDifference(string s, string t) {
        // XOR approach
        char result = (char)0;
        
        // XOR all characters in s
        foreach (char c in s) {
            result ^= c;
        }
        
        // XOR all characters in t
        foreach (char c in t) {
            result ^= c;
        }
        
        // The remaining value is the added character
        return result;
    }
}