Linkedin Interview - Isomorphic Strings

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Given two strings, determine if they are isomorphic. 

Two words are called isomorphic if the letters in one word can be remapped to get the second word. Remapping a letter means replacing all occurrences of it with another letter while the ordering of the letters remains unchanged. No two letters may map to the same letter, but a letter may map to itself.

Examples: 

Given 

'foo', 'app'

, returns 

true

We can map 

'f' -> 'a' and 'o' -> 'p'

Given 

'bar', 'foo'

, returns 

false

We can’t map both 

'a' and 'r'

 to 

'o'

Given 

'turtle', 'tletur'

, returns 

true

We can map 

't' -> 't', 'u' -> 'l', 'r' -> 'e', 'l' -> 'u', 'e' -'r'

Given 

'ab', 'ca'

, returns 

true

We can map 

'a' -> 'c', 'b' -> 'a'

 

public boolean is_isomorphic(String s, String t) {
if(s.length() != t.length()) return false;
Map<Character, Character> mapS = new HashMap<>(),
mapT = new HashMap<>();

for(int i=0; i<s.length(); i++) {
char cs = s.charAt(i);
char ct = t.charAt(i);
if(!mapS.containsKey(cs)) {
mapS.put(cs, ct);
} else if(mapS.get(cs) != ct) {
return false;
}

if(!mapT.containsKey(ct)) {
mapT.put(ct, cs);
} else if(mapT.get(ct) != cs) {
return false;
}
}
return true;
}