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isIsomorphic.java
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54 lines (50 loc) · 2.18 KB
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/**
* Compare 2 string and check whether they are isomorphic
* Two strings are isomorphic if the characters in s can be replaced to get t.
*/
//Idea: create a hashmap table
//For example,"egg" and "add" are isomorphic, "foo" and "bar" are not.
// a method for getting key of a target value (check key exists)
// This hash map table is created
// Get key given taget value
public Character getKey(HashMap<Character,Character> map, Character target) {
//Checking for loop
for (Map.Entry<Character,Character> entry : map.entrySet()) {
if (entry.getValue().equals(target)) { //if value === target given, then return the key
return entry.getKey();
}
}
return null;
}
//Checking for isomorphic between 2 arrays
//Let assume that S is key and t is value that need to mapped/compared to value stored by key
//Notice special case (null, empty string, string length not equal, return boolean right away)
public boolean isIsomorphic(String s, String t) {
if (s == null || t == null) { //If either of these string is empty, return false right away
return false;
}
if(s.length() != t.length()) { //If 2 strings are not equal in length, return false right away
return false;
}
if(s.length() == 0 && t.length() == 0) { //If both empty string, return true right away
return true;
}
//Create a hashmap to store mapping character
HashMap<Character, Character> map = new HashMap<Character,Character>();
//We only need to loop once since 2 array is equal in size
for(int i=0; i<s.length(); i++) {
char c1 = s.charAt(i); //s will be key
char c2 = t.charAt(i); //t will be value in hashmap
Character c = getKey(map, c2); //get key from value
if(c != null && c != c1) { //if key exist, but not the same as what we retrieve from s, return false
return false;
} else if(map.containsKey(c1)) { //map has key, but value is not equal
if(c2 != map.get(c1)) {
return false;
}
} else {
map.put(c1,c2); //put new key and hashmap and continue looping
}
}
return true; //If everything matched with key in hashmap, return true
}