LintCode之Strings Homomorphism

判断两个字符串的结构是否相同。

样例：
Given s = “egg”, t = “add”, return true.
Given s = “foo”, t = “bar”, return false.
Given s = “paper”, t = “title”, return true.

public static boolean isIsomorphic(String s, String t) {        String str1 = stringStructure(s);        String str2 = stringStructure(t);        if (str1.equals(str2)) {            return true;        }        return false;    }    public static String stringStructure(String s) {        List<String> list = new ArrayList<>();        for (int i = 0; i < s.length(); i++) {            if (!list.contains(s.charAt(i) + "")) {                list.add(s.charAt(i) + "");            }        }        StringBuffer sb = new StringBuffer();        for (int i = 0; i < s.length(); i++) {            for (int j = 0; j < list.size(); j++) {                if ((s.charAt(i)+"").equals(list.get(j))) {                    sb.append(j);                }            }        }        return sb+"";    }