Given two stringssandt, determine if they are isomorphic.
Two strings are isomorphic if the characters inscan be replaced to gett.
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.
这题厉害了， 利用map.put()的返回值来确定是否规则一致， 看代码！
