用int array记录可用字母数量

0的时候说明GG了

public boolean canConstruct(String ransomNote, String magazine) {        if(ransomNote.length() > magazine.length()) return false;        int[] letters = new int[26];                for(int n = 0; n < magazine.length();n++)        {            letters[magazine.charAt(n) - 'a']++;        }        for(int n = 0; n < ransomNote.length();n++)        {            if(letters[ransomNote.charAt(n) -'a'] != 0) letters[ransomNote.charAt(n)-'a']--;            else return false;        }        return true;    }