leetcode Isomorphic Strings

题目连接

https://leetcode.com/problems/isomorphic-strings/  

Isomorphic Strings

Description

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 {
private:
	typedef unordered_map<char, char> UMP;
public:
	bool isIsomorphic(string s, string t) {
		if (s == t) return true;
		UMP A, B;
		int n = s.length();
		for (int i = 0; i < n; i++) {
			char x1 = s[i], x2 = t[i];
			if (A.find(x1) == A.end()) A[x1] = x2;
			else if (A[x1] != x2) return false;
			if (B.find(x2) == B.end()) B[x2] = x1;
			else if (B[x2] != x1) return false;
		}
		return true;
	}
};