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.

Solution:

  1. public class Solution {
  2.   public boolean isIsomorphic(String s, String t) {
  3.     Map<Character, Character> map1 = new HashMap<>();
  4.     Map<Character, Character> map2 = new HashMap<>();
  6.     for (int i = 0; i < s.length(); i++) {
  7.       char c1 = s.charAt(i);
  8.       char c2 = t.charAt(i);
  10.       if (map1.containsKey(c1) && map1.get(c1) != c2)
  11.         return false;
  13.       if (map2.containsKey(c2) && map2.get(c2) != c1)
  14.         return false;
  16.       map1.put(c1, c2);
  17.       map2.put(c2, c1);
  18.     }
  20.     return true;
  21.   }
  22. }