leetcode-Isomorphic Strings

Difficulty: Easy

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.

class Solution {
public:
    bool isIsomorphic(string s, string t) {
        if(s.length()!=t.length())
            return false;
        int length=s.length();
        map<char,char> check;
        map<char,bool> tcheck;
        for(int i=0;i<length;++i){
            if(check.find(s[i])==check.end()&&tcheck[t[i]]==false){ //只能建立一对一的映射关系
                check[s[i]]=t[i];
                tcheck[t[i]]=true;
            }
            
        }
        for(int i=0;i<length;++i)
            s[i]=check[s[i]];
        
        return s==t;    
    }
};