leetcode 205

205. 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.

设定两个字符串长度相等，所谓的“同构”，就是字符串 s 中的字符可以一对一的映射到字符串 t 中的字符。不能一对多，也不能多对一。

利用两个map实现。

代码如下：                                

class Solution {
public:
    bool isIsomorphic(string s, string t) {
        map<char, char> mapA;
        map<char, char> mapB;
        int n = s.length();
        for(int i = 0; i < n; i++)
        {
            char ss = s[i];
            char tt = t[i];
            map<char, char>::iterator it = mapA.find(ss);
            if(it != mapA.end())
            {
                if(mapA[ss] != tt)
                {
                    return false;
                }
            }
            else
            {
                map<char, char>::iterator ii = mapB.find(tt);
                if(ii != mapB.end() && mapB[tt] != ss)
                {
                    return false;
                }
                else
                {
                    mapA[ss] = tt;
                    mapB[tt] = ss;
                }
            }
        }
        return true;
    }
};