205. Isomorphic Strings

题目分析

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这道题目让我们判断两个字符串是否是同构字符串。示例如下：

Given "egg", "add", return true.
Given "foo", "bar", return false.
Given "paper", "title", return true.

解题思路是用两个 Map 记录两个字符串中的字符的映射关系。

代码

class Solution {
    public boolean isIsomorphic(String s, String t) {
        Map<Character, Character> hm1 = new HashMap<Character, Character>();
        Map<Character, Character> hm2 = new HashMap<Character, Character>();
        for(int i = 0; i < s.length(); i++) {
            char c1 = s.charAt(i);
            char c2 = t.charAt(i);
            if(hm1.containsKey(c1)) {
                if(hm1.get(c1) != c2) {
                    return false;
                }
            }
            if(hm2.containsKey(c2)) {
                if(hm2.get(c2) != c1) {
                    return false;
                }
            }
            hm1.put(c1, c2);
            hm2.put(c2, c1);
        }
        return true;
    }
}