25- Find the Difference

The problem can be found at the following link: Question Link

My Approach

1. Initialize an unordered_map called mp to store character frequencies.

2. Iterate through each character c in string s:

   • Increment the count of character c in the mp map by 1.

   • This loop populates the mp map with the frequency of each character in string s.

3. Iterate through each character c in string t:

   • Decrement the count of character c in the mp map by 1.

   • Check if the count becomes less than 0. If it does, return the character c. This character is the one that appears more times in string t than in string s, making it the "difference" character.

4. If no difference character is found during the loop in step 3, return the null character '\0'. This indicates that all characters in s and t are the same, and there is no additional character in t.

Time and Auxiliary Space Complexity

• Time Complexity: O(n)

• Auxiliary Space Complexity: O(n)

Code (C++)

class Solution {
public:
    char findTheDifference(string s, string t) {
        unordered_map<char,int> mp;
        for(auto& c:s) mp[c]+=1;
        for(auto& c:t) if(--mp[c]<0) return c;
        return '\0';
    }
};

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