Isomorphic Strings

题目地址：
https://leetcode.com/problems/isomorphic-strings/description/

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.

解题思路：
这道题就是用map去重。

代码：

public boolean isIsomorphic(String s, String t) {
    Map<Character, Character> map = new HashMap<>();
    int len = s.length();
    for(int i = 0; i <= len - 1; i++){
        char cs = s.charAt(i);
        char ct = t.charAt(i);
        if(map.containsKey(cs)){
            if(map.get(cs) != ct){
                return false;
            }
        }
        else{
            if(map.values().contains(ct)){
                return false;
            }
            else{
                map.put(cs, ct);
            }
        }
    }
    return true;
}