leetcode 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.

思路：记录映射关系，如果不能匹配就返回false

class Solution {
public:
    bool isIsomorphic(string s, string t) {
        unordered_map<char, char> mp1;
        unordered_map<char, char> mp2;
        for (int i = 0; i < s.size(); ++i) {
            if (mp1.count(s[i]) == 0 && mp2.count(t[i]) == 0) {
                mp1[s[i]] = t[i];
                mp2[t[i]] = s[i];
            } else if (mp1.count(s[i]) == 0) {
                if (s[i] != mp2[t[i]]) return false;
            } else if (mp2.count(t[i]) == 0) {
                if (t[i] != mp1[s[i]]) return false;
            }
            else {
                if (mp2[t[i]] != s[i] || mp1[s[i]] != t[i]) return false;
            }
        }
        return true;
    }
}; 
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