LeetCode205 Isomorphic Strings

题目：

       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.

       Example 1:

       Input: s = "egg", t = "add"

       Output: true

       Example 2:

       Input: s = "foo", t = "bar"

       Output: false

       Example 3:

       Input: s = "paper", t = "title"

       Note:

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

public class IsomorphicString {
    public boolean isIsomorphic(String s, String t) {
        //init check
        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);

            if(map.containsKey(c1)) {
                if(map.get(c1) != c2) return false;
            } else {
                if(set.contains(c2)) return false;
                else {
                    map.put(c1, c2);
                    set.add(c2);
                }
            }
        }
        return true;
    }

    public static void main(String[] args) {
        String s = "egg";
        String t = "add";
        System.out.println(new IsomorphicString().isIsomorphic(s, t));
    }
}

public class IsomorphicString {
    public boolean isIsomorphic(String s, String t) {
        //init check
        if(s==null || t==null) return false;
        if(s.length() != t.length()) return false;

        char[] charArr1 = s.toCharArray();
        char[] charArr2 = t.toCharArray();
        char[] show1 = new char[255];
        char[] show2 = new char[255];
        for (int i = 0; i < charArr1.length; i++) {
            char c1 = charArr1[i];
            char c2 = charArr2[i];
            if (show1[c1] == 0 && show2[c2] == 0) {
                show1[c1] = c2;
                show2[c2] = c1;
            } else {
                if (show1[c1] != c2 || show2[c2] != c1) {
                    return false;
                }
            }
        }
        return true;
    }

    public static void main(String[] args) {
        String s = "egg";
        String t = "add";
        System.out.println(new IsomorphicString().isIsomorphic(s, t));
    }
}