LeetCode: 205. 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.

Note:
You may assume both s and t have the same length.

 

题目大意：判断两个相等长度的字符串是不是isomorphic，isomorphic的定义就是一个字符串的每个字符可以一一映射得到另一个字符串

 

思路：可以用一个hashmap来存储对应字符的映射关系，但是要注意映射是一对一，不能多对一，不能一对多

 

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

 

也可以用两个256大小的数组来标记关系