Leetcode: 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 gett.

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.

注意不同的字符不能映射到同一个字符这个条件。

class Solution {public:    bool isIsomorphic(string s, string t) {        unordered_map<char, char> charMapping;        unordered_set<char> occupied;        for (int i = 0; i < s.size(); ++i) {            auto iter = charMapping.find(s[i]);            if (iter == charMapping.end()) {                if (occupied.find(t[i]) == occupied.end()) {                    charMapping.emplace(s[i], t[i]);                    occupied.emplace(t[i]);                }                else {                    return false;                }            }            else {                if (t[i] != iter->second) {                    return false;                }            }        }                return true;    }};