205.cpp

class Solution {
public:
    bool isIsomorphic(string s, string t) {
        map<char, char> m1;
        map<char, char> m2;
        bool flag = true;
        for(int i = 0; i < s.size(); i++) {
            if (m1.find(s[i]) == m1.end() && m2.find(t[i]) == m2.end()) {
                m1[s[i]] = t[i];
                m2[t[i]] = s[i];
            } else if (m1.find(s[i]) != m1.end() && m2.find(t[i]) != m2.end()) {
                if (m1[s[i]] != t[i] || m2[t[i]] != s[i]) {
                    flag = false;
                    break;
                }
            } else {
                flag = false;
                break;
            }
        }
        return flag;
    }
};