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;
}
};