leetcode Isomorphic Strings

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.

没做出来。

没有非常清楚的理解题目的意思，题目是说，两个字符串同构。我却认为是只要字符串s中哪些字符串一样，t中相同位置的字符串也要一样。

事实上约束更多，讲的是一种映射，就如同egg,e与a映射，g与d映射，那么字符串s中如果再出现e，字符串t中就必须是a。

所以，构建一个map，用上次见过的方法就行了。if（map.find(s[i])==map.end()）****else****

不过需要有两次检查，检查s->t的映射t是否满足，还有t->s的映射s是否满足。

 1 class Solution {
 2 public:
 3     bool isIsomorphic(string s, string t) {
 4         map<char,char> model;
 5         int slength=s.length(),tlength=t.length();
 6         if(slength!=tlength) return false;
 7         for(int i=0;i<slength;i++){
 8             if(model.find(s[i])==model.end()) model[s[i]]=t[i];
 9             else if(model[s[i]]!=t[i]) return false;
10         }
11         model.clear();
12         for(int i=0;i<slength;i++){
13             if(model.find(t[i])==model.end()) model[t[i]]=s[i];
14             else if(model[t[i]]!=s[i]) return false;
15         }
16         return true;
17 
18         
19     }
20 };