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.

Example 1:

Input: s = “egg”, t = “add”
Output: true
Example 2:

Input: s = “foo”, t = “bar”
Output: false
Example 3:

Input: s = “paper”, t = “title”
Output: true
Note:
You may assume both s and t have the same length.

将两个字符串分别放入一个map里，每次判断map里的值是否符合预期。

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

此解法的空间使用较大，但暂未想到使用空间小的方式。

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