剑指 Offer II 034. 外星语言是否排序

class Solution {
    public boolean isAlienSorted(String[] words, String order) {
        if (words == null || words.length == 0 || order == null || order.length() == 0) return false;
        Map<Character, Integer> index = new HashMap<>();
        for (int i = 0; i < order.length(); i++) {
            index.put(order.charAt(i), i);
        }
        for (int i = 0; i < words.length - 1; i++) {
            if (!inOrder(words[i], words[i + 1], index)) return false;
        }
        return true;
    }
    private boolean inOrder(String s1, String s2, Map<Character, Integer> index) {
        int minLen = Math.min(s1.length(), s2.length());
        for (int i = 0; i < minLen; i++) {
            char c1 = s1.charAt(i), c2 = s2.charAt(i);
            if (c1 != c2) {
                if (index.get(c1) > index.get(c2)) {
                    return false;
                } else {
                    return true;
                }
            }
        }
        if (s1.length() > s2.length()) return false;
        return true;
    }
}