Leetcode题目：Isomorphic Strings

题目：

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

题目解答：判断两个单词是否是同构的。需要两个map，分别控制s到t和t到s的映射关系。

代码如下：

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