leetcode205---Isomorphic Strings（相同结构的字符串）

问题描述：

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.

问题求解：利用两个hash表

class Solution {public:    bool isIsomorphic(string s, string t) {        unordered_map<char, int> um1;        unordered_map<char, int> um2;        for(int i=0;i<s.length();i++)        {//hash映射.如"egg", "add"，相同位置处字母索引相同         //对于每个字符串，相同字母对应的索引累加。            um1[s[i]] += i+1;            um2[t[i]] += i+1;        }//若字符串结构相同，则每个字符对应hash映射也应相同        for(int j=0;j<s.length();j++)        {            if(um1[s[j]] != um2[t[j]]) return false;        }        return true;    }};