Isomorphic Strings

Source

• leetcode: 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.

Java

public class Solution {
    public boolean isIsomorphic(String s, String t) {
        if(s.length()!=t.length()) return false;  
        HashMap<Character,Character> map1=new HashMap<Character, Character>();  
        HashMap<Character,Character> map2=new HashMap<Character, Character>();  

        for(int i=0;i<s.length();i++){  
            char c1=s.charAt(i);  
            char c2=t.charAt(i);  
            if(map1.containsKey(c1)){  
                if(map1.get(c1)!=c2) return false;  
            }  
            if(map2.containsKey(c2)){  
                if(map2.get(c2)!=c1) return false;  
            }  

            map1.put(c1, c2);  
            map2.put(c2, c1);  
        }  
        return true; 
    }
}

Python

class Solution(object):
    def isIsomorphic(self, s, t):
        """
        :type s: str
        :type t: str
        :rtype: bool
        """
        if len(s)!=len(t):
            return False

        map1= {}
        map2 = {}

        for i in range(len(s)):
            c1 = s[i]
            c2 = t[i]

            if c1 in map1:
                if map1[c1] != c2:
                    return False

            if c2 in map2:
                if map2[c2] != c1:
                    return False

            map1[c1] = c2
            map2[c2] = c1

        return True