leetcode 383. Ransom Note

class Solution {
public:
    bool canConstruct(string ransomNote, string magazine) {
       int a[26]={0};
       for(int i = 0;i < ransomNote.length(); i++)
            a[ransomNote[i]-'a']++;
        for(int i = 0;i < magazine.length(); i++)
            a[magazine[i]-'a']--;
        for(int i = 0;i < 26; i++)
            if(a[i] > 0) return false;
        return true;
    }
};