[LeetCode] 205. Isomorphic Strings 解题思路

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.

问题：给定两个字符串，判断他们是否同构。

当字符串 s 中的字符可以被替换得到另一个字符串 t , 则表示字符串 s 和 t 是同构。

import static java.lang.System.out;

import java.util.Hashtable;

public class Solution {
    public boolean isIsomorphic(String s, String t) {
        
        Hashtable<Character, Character> s_t = new Hashtable<Character, Character>();
        Hashtable<Character, Character> t_s = new Hashtable<Character, Character>();
        
        int length = s.length();
        for(int i = 0; i < length; i++){

            Character ss = s.charAt(i);
            Character tt = t.charAt(i);
            
            if(s_t.containsKey(ss) || t_s.containsKey(tt)){                                
                if(s_t.get(ss) == tt && t_s.get(tt) == ss){
                    continue;
                }else{
                    return false;
                }
            }else{
                s_t.put(ss, tt);
                t_s.put(tt, ss);
            }
        }        
        return true;
    }
}