題目描述：
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.
Example 1:
Input: s ="egg",t ="add"Output: true
Example 2:
Input: s ="foo",t ="bar"Output: false
Example 3:
Input: s ="paper",t ="title"Output: true
程序：
class Solution {
public:
bool isIsomorphic(string s, string t) {
if(s.size() != t.size()) return false;
map<char,char> mp;
map<char,bool> hasmp;
for(int i = 0; i < s.size(); i++){
if(mp.find(s[i]) == mp.end()){
if(hasmp[t[i]]) return false;
mp[s[i]] = t[i];
hasmp[t[i]] = true;
}
else if(mp[s[i]] != t[i]) return false;
}
return true;
}
};