[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.

 

     个人觉得挺有意思的一道题。首先要理解到底啥才叫lsomorphic strings。归纳出其的特点。

     其实就是字母可以不相同，但是结构必须相同。就是说对于string s，其出现重复字母的index必须和string t，出现重复的字母的index相等而且数量也相同。

     搞清楚这个就可以用if statement来写判断了。

      代码如下。~

 

public class Solution {
    public boolean isIsomorphic(String s, String t) {
        if(s.length()!=t.length()) return false;
        HashMap<Character,Integer> smap=new HashMap<>();
        HashMap<Character,Integer> tmap=new HashMap<>();
        for(int i=0;i<s.length();i++){
            if(!smap.containsKey(s.charAt(i))){
                if(tmap.containsKey(t.charAt(i))){
                    return false;
                }
            }else{
                int index=smap.get(s.charAt(i));
                if(!tmap.containsKey(t.charAt(i))||tmap.get(t.charAt(i))!=index){
                    return false;
                }
            }
            smap.put(s.charAt(i),i);
            tmap.put(t.charAt(i),i);
        }
        return true;
    }
}