# C#LeetCode刷题之#205-同构字符串（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.

Input: s = “egg”, t = “add”

Output: true

Input: s = “foo”, t = “bar”

Output: false

Input: s = “paper”, t = “title”

Output: true

Note:You may assume both s and t have the same length.

```public class Program {

public static void Main(string[] args) {
var s = "egg";
var t = "add";

var res = IsIsomorphic(s, t);
Console.WriteLine(res);

}

private static bool IsIsomorphic(string s, string t) {
var dic = new Dictionary<int, int>();
for(var i = 0; i < s.Length; i++) {
if(!dic.ContainsKey(s[i])) {
if(dic.ContainsValue(t[i])) return false;
dic[s[i]] = t[i];
}
}
for(var i = 0; i < s.Length; i++) {
if(dic[s[i]] != t[i]) return false;
}
return true;
}

}```

`True`

(2)