【LeetCode】205. Isomorphic Strings

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.

 

返回true需要滿足兩個條件：

1、不能出現s中的一個字符對應到t中兩個不同的字符

2、不能出現s中的兩個不同字符對應到t中同一個字符

class Solution {
public:
    bool isIsomorphic(string s, string t) {
        int m = s.size();
        int n = t.size();
        if(m != n)
            return false;
        unordered_map<char, char> m1;   //s --> t
        unordered_map<char, char> m2;   //t --> s
        for(int i = 0; i < m; i ++)
        {
            char schar = s[i];
            char tchar = t[i];
            // the same char in s map to different chars in t
            if(m1.find(schar) != m1.end() && m1[schar] != tchar)
                return false;
            // two different chars in s map tp the same char in t
            if(m2.find(tchar) != m2.end() && m2[tchar] != schar)
                return false;
            m1[schar] = tchar;
            m2[tchar] = schar;
        }
        return true;
    }
};