leetcode 205. Isomorphic Strings

Title Description ：

Given two strings s and t , Judge whether they are isomorphic .

If s The characters in can be replaced according to some mapping relationship t , So these two strings are isomorphic .

Every character that appears should be mapped to another character , Without changing the order of characters . Different characters cannot be mapped to the same character , The same character can only be mapped to the same character , Characters can be mapped to themselves .

Examples ：

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"
Output ：true

Tips ：

    1 <= s.length <= 5 * 104
    t.length == s.length
    s and t By any valid ASCII Character composition

Java Program ：

class Solution {
    public boolean isIsomorphic(String s, String t) {
        Map<Character, Character> s2t = new HashMap<Character, Character>();
        Map<Character, Character> t2s = new HashMap<Character, Character>();
        int len = s.length();
        for (int i = 0; i < len; ++i) {
            char x = s.charAt(i), y = t.charAt(i);
            if ((s2t.containsKey(x) && s2t.get(x) != y) || (t2s.containsKey(y) && t2s.get(y) != x)) {
                return false;
            }
            s2t.put(x, y);
            t2s.put(y, x);
        }
        return true;
    }
}