开始刷leetcode day1：Isomorphic Strings

题目：

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.

Java version

public class Solution {

public boolean isIsomorphic(String s, String t) {

HashMap<Character, Character> hashmap = new HashMap<Character,Character>();

HashMap<Character, Character> hashmap2 = new HashMap<Character,Character>();

char[] slist = s.toCharArray();

char[] tlist = t.toCharArray();

for(int i = 0; i< s.length(); i++)

{

if(hashmap.get(slist[i]) == null)

{

if(hashmap2.get(tlist[i]) != null)

return false;

hashmap.put(slist[i],tlist[i]);

hashmap2.put(tlist[i],slist[i]);

}

else if(hashmap.get(slist[i]) != tlist[i])

{

return false;

}else

{

//doing nothing when equals

}

}

return true;

}

}

笨办法，有待改进， 需要注意情况ab aa应该返回false，所以需要第二个hashmap，用来反向检查