LeetCode: 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.

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.

class Solution {
public:
bool isIsomorphic(string s, string t) {
if(s.size() != t.size())
return false;
unordered_map<char, char> m_map;
unordered_map<char, bool> dulplicate;
for(int i = 0; i < s.size(); i++)
{
if(m_map.find(s[i]) == m_map.end())
{
if(dulplicate[t[i]] == true)
return false;
m_map[s[i]] = t[i];
dulplicate[t[i]] = true;
}
else
{
if(m_map[s[i]] != t[i])
return false;
}
}
return true;
}
};