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;
}
}