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.
一刷
很简单的思路，map。但是注意字母和字母之间只能是一一对应的关系，不能出现一对多。用set或者boolean array来解决都可以。
public class Solution {
public boolean isIsomorphic(String s, String t) {
if(s.length() == 0 && t.length() == 0) return true;
if(s.length()!=t.length()) return false;
Map<Character, Character> map = new HashMap<>();
for(int i=0; i<s.length(); i++){
char ss = s.charAt(i);
char tt = t.charAt(i);
if(map.containsKey(ss)){
if(tt!=map.get(ss)) return false;
}
else{
map.put(ss, tt);
}
}
//in case that multiple character map to the same
Set<Character> set = new HashSet<>();
for(char ch : map.values()){
if(set.contains(ch)) return false;
else set.add(ch);
}
return true;
}
}
