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.

看两个字符串是否同构,用map就可以解决，不过要注意双向都要检查，代码如下：

1 class Solution { 2 public: 3     bool isIsomorphic(string s, string t) { 4         map
     
       m1; 5         map
      
        m2; 6         if(s.size() != t.size()) 7             return false; 8         for(int i = 0; i < s.size(); ++i){ 9             if(m1.find(s[i]) == m1.end() && m2.find(t[i]) == m2.end()){10                 m1[s[i]] = t[i];11                 m2[t[i]] = s[i];12             }13             else if(m1.find(s[i]) != m1.end() && m2.find(t[i]) != m2.end()){14                 if(m1[s[i]] != t[i] || m2[t[i]] != s[i])15                     return false;16             }else{17                 return false;18             }19         }20         return true;21     }22 };