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) { int m = s.size(); int n = t.size(); if(m != n) return false; unordered_map<char, char> m1; //s --> t unordered_map<char, char> m2; //t --> s for(int i = 0; i < m; i ++) { char schar = s[i]; char tchar = t[i]; // the same char in s map to different chars in t if(m1.find(schar) != m1.end() && m1[schar] != tchar) return false; // two different chars in s map tp the same char in t if(m2.find(tchar) != m2.end() && m2[tchar] != schar) return false; m1[schar] = tchar; m2[tchar] = schar; } return true; }};原文：http://www.cnblogs.com/dylqt/p/5587376.html