Java for LeetCode 205 Isomorphic Strings

Given two strings s and t, determine if they are isomorphic.

Two strings are isomorphic if the characters in s can be replaced to get t.

All occurrences of a character must be replaced with another character while preserving the order of characters. No two characters may map to the same character but a character may map to itself.

For example,
Given "egg", "add", return true.

Given "foo", "bar", return false.

Given "paper", "title", return true.

解题思路：

用两张图保存下两个方向的映射即可，JAVA实现如下：

    public boolean isIsomorphic(String s, String t) {
		HashMap<Character, Character> hm = new HashMap<Character, Character>();
		HashMap<Character, Character> hm2 = new HashMap<Character, Character>();
		for (int i = 0; i < s.length(); i++) {
			if (hm.containsKey(s.charAt(i))
					&& hm.get(s.charAt(i)) != t.charAt(i))
				return false;
			hm.put(s.charAt(i), t.charAt(i));
			if (hm2.containsKey(t.charAt(i))
					&& hm2.get(t.charAt(i)) != s.charAt(i))
				return false;
			hm2.put(t.charAt(i), s.charAt(i));
		}
		return true;
    }