leetcode-859-easy

Buddy Strings
思路一: 两个字符是 Buddy Strings 的完全分类

• 字符不一样 && 只存在两个位置交换的字符
• 字符一样 && 存在重复的字符

按照上面的分类，记录两个不同位置的下标和统计出现字符的情况

public boolean buddyStrings(String s, String goal) {
    if (s.length() != goal.length()) return false;

    int[] count = new int[26];
    boolean find = false;
    int first = -1;
    int second = -1;

    for (int i = 0; i < s.length(); i++) {
        if (s.charAt(i) != goal.charAt(i)) {
            if (first == -1) {
                first = i;
                continue;
            }

            if (second == -1) {
                second = i;
            } else {
                return false;
            }
        }
        count[s.charAt(i) - 'a']++;
        if (count[s.charAt(i) - 'a'] >= 2) find = true;
    }

    if (first == -1 && second == -1 && find) return true;

    return first != -1 && second != -1 &&
            s.charAt(second) == goal.charAt(first)
            && s.charAt(first) == goal.charAt(second);
}