Leetcode 题目解析之 Isomorphic Strings

    public boolean isIsomorphic(String s, String t) {
        if (s == null || t == null) {
            return false;
        }
        if (s.length() != t.length()) {
            return false;
        }
        Map<Character, Character> map = new HashMap<Character, Character>();
        Set<Character> set = new HashSet<Character>();
        for (int i = 0; i < s.length(); i++) {
            char c1 = s.charAt(i);
            char c2 = t.charAt(i);
            // 保证一对一的映射关系
            if (map.containsKey(c1)) {
                if (map.get(c1) != c2) {
                    return false;
                }
            } else {
                if (set.contains(c2)) {
                    return false;
                }
                map.put(c1, c2);
                set.add(c2);
            }
        }
        return true;
    }