String - 205. Isomorphic Strings

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.

思路：

因为char的范围是-127-128，字符串中的字符都在ASCII表中。使用两个128位的数组来记录每一位字母在字符串中出现的次数就够了。

代码：

java：

class Solution {

    public boolean isIsomorphic(String s, String t) {
        int[] m1 = new int[128];
        int[] m2 = new int[128];
        char[] str1 = s.toCharArray();
        char[] str2 = t.toCharArray();
        
        for (int i = 0; i < s.length(); i++) {
            if (m1[str1[i]] != m2[str2[i]]) return false;
            m1[str1[i]] = m2[str2[i]] = i+1;
        }
        
        return true;
    }
}