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.

判断一个字符串是否可以替换为另一个字符串

C++(6ms):

class Solution {
public:
    bool isIsomorphic(string s, string t) {
        vector<int> map_s(128,0) ;
        vector<int> map_t(128,0) ;
        for(int i = 0 ; i < s.size() ; i++){
            if(map_s[s[i]] != map_t[t[i]]){
                return false ;
            }
            map_s[s[i]] = i+1 ;
            map_t[t[i]] = i+1 ;
        }
        return true ;
    }
};

Java(7ms):

public class Solution {
    public boolean isIsomorphic(String s1, String s2) {
        int[] m1 = new int[128];
        int[] m2 = new int[128];
        for (int i = 0; i < s1.length(); i++) {
            if (m1[s1.charAt(i)] != m2[s2.charAt(i)]) 
                return false;
            m1[s1.charAt(i)] = i+1 ;
            m2[s2.charAt(i)] = i+1 ;
        }
        return true;
    }
}