题目描述:(链接)
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.
解题思路：
用哈希表来存储字符出现的位置，然后比较同型字符出现的位置，如果不等返回false。
1 class Solution { 2 public: 3 bool isIsomorphic(string s, string t) { 4 int len = s.size(); 5 6 unordered_map<int, int> cache1; 7 unordered_map<int, int> cache2; 8 for (int i = 0; i < len; ++i) { 9 auto c1 = cache1.find(s[i]); 10 auto c2 = cache2.find(t[i]); 11 12 if (c1 == cache1.end() && c2 == cache2.end()) { 13 cache1[s[i]] = i; 14 cache2[t[i]] = i; 15 } else if ((c1 == cache1.end() && c2 != cache2.end()) || 16 (c1 != cache1.end() && c2 == cache2.end()) || 17 (c1->second != c2->second)) { 18 return false; 19 } 20 } 21 22 return true; 23 } 24 };
原文：http://www.cnblogs.com/skycore/p/4965243.html