LeetCode-859 Buddy Strings Solution (with Java)

1. Description:

Notes:

2. Examples:

3.Solutions:

/**
 * Created by sheepcore on 2018-12-24
 */
class Solution {
    public boolean buddyStrings(String s1, String s2) {
        if (s1.equals(s2))
            return isLetterShowTwice(s1) ? true : false;
        else if (s1.length() != s2.length())
            return false;
        char[] str = new char[4];
        int flag = 0;
        for (int i = 0; i < s1.length(); i++)
            if (s1.charAt(i) != s2.charAt(i))
                if (flag < 4) {
                    str[flag] = s1.charAt(i);
                    //System.out.println(s1.charAt(i));
                    str[flag + 1] = s2.charAt(i);
                    //System.out.println(s2.charAt(i));
                    flag += 2;
                } else
                    return false;
        return (str[0] == str[3] && str[1] == str[2]) ? true : false;
    }

    public  boolean isLetterShowTwice(String s) {
            byte[] alphate = new byte[26];
        for (char ch : s.toCharArray()) {
            alphate[ch - 'a']++;
            if (alphate[ch - 'a'] > 1)
                return true;
        }
        return false;
    }
}