205. Isomorphic Strings

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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.

 

//Time: O(n), Space: O(n)    public boolean isIsomorphic(String s, String t) {        if (s == null && t == null) {            return true;        }                if (s == null || t == null) {            return false;        }                if (s.length() != t.length()) {            return false;        }                int[] mapS = new int[256];        int[] mapT = new int[256];                for (int i = 0; i < s.length(); i++) {            if (mapS[s.charAt(i)] != mapT[t.charAt(i)]) {                return false;            }            mapS[s.charAt(i)] = i + 1;//反例就是ab和aa,否則無法判斷第一位有無出現過            mapT[t.charAt(i)] = i + 1;        }                return true;    }

 

205. Isomorphic Strings