Leetcode:Isomorphic Strings(hash table) solution

Isomorphic Strings

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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.

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 Hash Table

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Using two map to maintain the mapping information, where the mapping is identified by the same second value, e.g.:

unordered_map<char, int> tmp1, tmp2;
tmp1[s[i]] = i;
tmp2[t[i]] = i;



///////////////////////////////////////////////////////////////////////
// code
class Solution {

class Solution {

public:

       bool isIsomorphic(string s, string t) {

              unordered_map<char, int> tmp1, tmp2;

              for (int i = 0; i<s.size(); i++){

                     //check the current item in the pool

                     //if not exist

                     if (tmp1.find(s[i]) == tmp1.end() && tmp2.find(t[i]) != tmp2.end())return false;

                     if (tmp1.find(s[i]) != tmp1.end() && tmp2.find(t[i]) == tmp2.end())return false;

                     //if exist

                     if (tmp1.find(s[i]) != tmp1.end() && (tmp1[s[i]]) != (tmp2[t[i]]))return false;

                     //fill the map

                     tmp1[s[i]] = i;

                     tmp2[t[i]] = i;

                     //check duplication

                     if (tmp1.size() != tmp2.size())return false;

              }

              return true;

       }

};