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.

Note:

You may assume both s and t have the same length.

注意用例"ab","aa"。

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