Find the Difference

class Solution {
public:
    char findTheDifference(string s, string t) {
        int alp[2][26];
        fill(&alp[0][0], &alp[1][26], 0);
        for (auto& c: s) {
            alp[0][c - 'a']++;
        }
        for (auto& c: t) {
            alp[1][c - 'a']++;
        }
        for(int i = 0; i < 26; i++) {
            if (alp[0][i] != alp[1][i]) {
                return static_cast<char>('a' + i);
            }
        }
        return 'a';
    }
};

//O(|s|) - time and memory complexity