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.

這題厲害了， 利用map.put()的返回值來確定是否規(guī)則一致， 看代碼！