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.

解法：

代码如下：

public class Solution {

    public boolean isIsomorphic(String s, String t) {

         int []m1 = new int[256];

         int []m2 = new int[256];

         int len  = s.length();

        for (int i = 0; i < len; ++i) {

            int m=s.charAt(i);

            int n=t.charAt(i);

            if(m1[m]!=m2[n])

              return false;

            m1[m] = i + 1;

            m2[n] = i + 1;

        }

        return true;

    }

}

运行结果：